Exam Questions Flashcards

Question

G0B13: What must you do when powering your house from an emergency generator? A. Disconnect the incoming utility power feed B. Insure that the generator is not grounded C. Insure that all lightning grounds are disconnected D. All of these choices

Answer 1

A: If you do not disconnect your home's circuit breaker box from the incoming power line, called backfeeding, the power from your generator will flow back to the utility lines where it creates a shock hazard for utility workers. In addition, if utility power is restored with your generator connected to the power line, the generator may be damaged.

Answer 2

C: The National Electrical Code covers the wiring of electrical devices,

Answer 3

A: Carbon monoxide and other exhaust fumes can accumulate in your garage, basement or other confined living area, so ventilation is very important. Be sure not to place generators near air intakes or vents, as well.

Answer 4

C: You need to keep your lead-acid battery charged at all times for use in an emergency. A by-product of charging your battery is the release of hydrogen gas that can explode if ignited by a spark. A well-ventilated area is essential.

Answer 5

C: These are the bands on which the entire range of mode-restricted segments (such as phone or CW/data) are open to all license classes that have access to the band. Generals, Advanced, and Extra Class licensees all have access to the entire band. [97.301(d), 97.303(s)]

Answer 6

B: The 30 meter band is restricted to CW, RTTY and data transmissions only. [97.305]

Answer 7

B: The 30 meter band is restricted to CW, RTTY and data transmissions only. Image transmission is also prohibited on the 60 meter band. [97.305]

Answer 8

D: In the US, Amateur Radio is a secondary service to government stations on 60 meters. By limiting amateur operation to specific channels, it is easier for hams to tell when government stations are present and to avoid interfering with them. [97.303(s)]

Answer 9

A: General Class licensees have access to the following portions of the 40 meter band (f = 300 / 40 = 7.5 MHz): 7.025 - 7.125 MHz on CW/RTTY/data and from 7.175 - 7.300 MHz on CW/Phone/Image. [97.301(d)]

Answer 10

D: Use the formula f = 300 / 12 = 25 MHz to get the approximate frequency range of the 12 meter band. [97.301(d)]

Answer 11

C: Although the 75 and 80 meter bands are part of a single amateur band, the difference in wavelength is enough for amateurs to make a distinction between 75 meters at the higher frequencies and 80 meters at the lower frequencies. General Class licensees have access to the following portions of the 75 meter band (f = 300 / 75 = 4.0 MHz): 3.800 - 4.000 MHz on CW/Phone/Image. [97.301(d)]

Answer 12

C: General Class licensees have access to the following portions of the 20 meter band (f = 300 / 20 = 15 MHz): 14.025 - 14.150 MHz on CW/Phone/image and from 14.225 - 14.350 MHz on CW/Phone/Image. [97.301(d)]

Answer 13

C: General Class licensees have access to the following portions of the 80 meter band (f = 300 / 80 = 3.75 MHz): 3.525 - 3.600 MHz on CW/RTTY/Data. [97.301(d)]

Answer 14

C: General Class licensees have access to the following portions of the 15 meter band (f = 300 / 15 = 20 MHz): 21.025 - 21.200 MHz on CW/RTTY/data and from 21.275 - 21.450 MHz on CW/Phone/Image. [97.301(d)]

Answer 15

D: The 28 MHz (10 meter) band is one of the bands on which the entire range of mode-restricted segments (such as phone or CW/data) are open to all license classes that have access to the band. Generals, Advanced, and Extra Class licensees all have access to the entire band. [97.301(d)]

Answer 16

B: If you look at the US Amateur Band chart available in the General Class License Manual or on the ARRL Web site at www.arrl.org/files/file/Hambands_color.pdf you will see that in the bands on which there are mode-restricted segments, such as 80 meters, General Class licensees have access to the higher frequencies of the segment. [97.301]

Answer 17

D: Citizens Band operators may not operate on amateur bands or on any frequency not assigned to the Citizens Radio Service. [97.303]

Answer 18

C: You should always listen before you transmit. This is especially important on bands where Amateur Radio is a secondary service, such as the 30 or 60 meter band. Amateurs are only permitted to use these frequencies if they do not cause harmful interference to the primary users. If you hear a station in the primary service or receive interference from such a station you should immediately change frequencies. Otherwise you might be causing interference to the primary station. [97.303]

Answer 19

D: You should always listen before you transmit. This is especially important on bands where Amateur Radio is a secondary service, such as the 30 or 60 meter band. Amateurs are only permitted to use these frequencies if they do not cause harmful interference to the primary users. If you hear a station in the primary service or receive interference from such a station you should immediately change frequencies. Otherwise you might be causing interference to the primary station. [97.303]

Answer 20

C: FCC regulations require approval if your antenna would be more than 200 feet above ground level at its site. This includes the antenna, the supports and anything else attached to the structure. (Additional FCC restrictions apply if the antenna is within about 4 miles of a public use airport or heliport.)[97.15(a)]

Answer 21

D: A beacon station normally transmits a signal for operators to observe propagation and reception characteristics. For this purpose, FCC rules specifically allow an amateur beacon to transmit one-way communications. [97.203(b)]

Answer 22

A: A beacon station normally transmits a signal for operators to observe propagation and reception characteristics. For this purpose, FCC rules specifically allow an amateur beacon to transmit one-way communications. [97.3(a)(9)]

Answer 23

A: Amateurs are not allowed to be involved with any activity related to program production or news gathering for broadcasting to the general public unless it is directly related to an emergency involving an immediate life or property-threatening situation and there is no other method by which the information can be transmitted. If there is an alternative communication system available, even if it is slower, the amateur station may not transmit the information for a news broadcast or related program production. [97.113(b)]

Answer 24

D: Normally, music may not be transmitted by an amateur station. This is to avoid infringing upon commercial broadcast activities. Music is often used in communications between ground control and the space shuttle or International Space Station (ISS) for such things as waking up the astronauts in the morning. In this case, since it is an incidental part of the transmission and not the primary purpose of it, the music can be retransmitted by the amateur station along with the rest of the space shuttle transmission, as long as the Amateur station has NASA’s permission to retransmit the Shuttle (or ISS) audio. [97.113(a)(5), 97.113(e)]

Answer 25

B: An amateur station may never transmit in such a manner as to obscure the meaning of two-way communication. The use of standard abbreviations does not violate this rule, since their meaning is well known. The exception is space telecommand operations where the commands and data may be coded. (This helps prevent unauthorized stations from transmitting telecommand messages to the spacecraft.) When controlling a satellite from a ground station, the transmissions may consist of specially coded messages intended to facilitate communications or related to the function of the spacecraft. Telecommand is not two-way communication, however; it is one-way communication. [97.113(a)(4), 97.207(f)]

Answer 26

B: The use of common abbreviations and procedural signals is standard practice and does not obscure the meaning of a message because their meaning is well known. Any use of abbreviations or codes for the purpose of obscuring the meaning of a communication is prohibited. [97.113(a)(4)]

Answer 27

D: Choosing a frequency is straightforward: Be sure the frequency is authorized to General class licensees, follow the band plan under normal circumstances, and listen to the frequency to avoid interfering with ongoing communications.

Answer 28

A: In general, amateurs are forbidden to receive any kind of compensation, financial or otherwise, for conducting communications on amateur frequencies. Amateurs are, however, permitted to conduct a limited amount of personal business, such as participating in “swap-and-shop” nets conducted on amateur frequencies for local amateurs to buy, sell and trade amateur equipment. [97.113(a)(3)]

Answer 29

C: 100 watts of output power is a good compromise, enabling a beacon station to transmit a signal strong enough to be heard when propagation isn’t the best. Similarly, when propagation is good, a 100-watt signal is not so strong as to cause interference to stations on nearby frequencies. [97.203(c)]

Answer 30

C: The FCC Rules grant amateurs a lot freedom in the ways they choose to operate, more than in any other service. It is impossible for the service’s broad rules and regulations to cover every situation that might possibly arise. You are expected to use common sense in those situations where an exact rule does not apply. Your station and its operation should always follow good engineering design and good amateur practice. [97.101(a)]

Answer 31

A: The FCC does not publish a list of what constitutes “good engineering and good amateur practice” because the state of the radio art is continually improving. Nevertheless, when questions arise, the FCC is the agency that determines what standards should be applied. [97.101(a)][97.101(a)]

Answer 32

A: The general rule is that maximum power is limited to 1500 watts PEP output, although there are exceptions where less power is allowed. One such exception is the 30 meter band, 10.100 - 10.150 MHz, where the maximum power for US hams is 200 watts. (These frequencies are just above the short-wave time broadcasts of WWV and WWVH at 10.0 MHz.) [97.313(c)(1)]

Answer 33

C: The maximum power allowed is 1500 watts PEP output from 24.890 - 24.990 MHz. [97.313(a), 97.313(b)]

Answer 34

A: The FCC Rules for operating on the amateur 60 meter band tell us that “Amateur stations must ensure that their transmission occupies only the 2.8 kHz centered around each” of the operating channels. So the maximum transmitted bandwidth of your upper sideband signal (the only operating mode allowed on this band) is 2.8 kHz. A properly adjusted SSB transmitter normally has a bandwidth of 2.5 to 2.8 kHz. [97.303(s)]

Answer 35

A: Although the maximum power allowed is 1500 watts PEP output, amateurs should use only the power level needed to carry out communications. [97.313(a)]

Answer 36

C: The maximum power allowed is 1500 watts PEP output on the entire band. [97.313(b)]

Answer 37

D: The maximum power allowed is 1500 watts PEP output on the entire band. [97.313(b)]

Answer 38

D: The symbol rate of digital signals is restricted to make sure they do not consume too much bandwidth at the expense of other modes. Table G1-1 shows the limits by band. [97.305(c), 97.307(f)(3)] {br/}{br/}{image src='Table G1-1.png'}

Answer 39

D: The symbol rate of digital signals is restricted to make sure they do not consume too much bandwidth at the expense of other modes. Table G1-1 shows the limits by band. [97.307(f)(3)] {br/}{br/}{image src='Table G1-1.png'}

Answer 40

A: The symbol rate of digital signals is restricted to make sure they do not consume too much bandwidth at the expense of other modes. Table G1-1 shows the limits by band. [97.305(c), 97.307(f)(5)] {br/}{br/}{image src='Table G1-1.png'}

Answer 41

C: The symbol rate of digital signals is restricted to make sure they do not consume too much bandwidth at the expense of other modes. Table G1-1 shows the limits by band. [97.305(c), 97.307(f)(4)] {br/}{br/}{image src='Table G1-1.png'}

Answer 42

B: The symbol rate of digital signals is restricted to make sure they do not consume too much bandwidth at the expense of other modes. Table G1-1 shows the limits by band. [97.305(c), 97.307(f)(5)] {br/}{br/}{image src='Table G1-1.png'}

Answer 43

C: You must add a “temporary identifier” to your call sign so that stations receiving your transmissions can verify that you are authorized to transmit on that frequency. If a temporary identifier was not used between the time you pass your exam and the time at which your new privileges appear in the FCC database, it would appear that you were transmitting on a frequency for which you were not authorized. When you upgrade to Extra class, you’ll append “temporary AE” to your call sign. [97.119(f)(2)]

Answer 44

C: Holders of a General class operator license may only administer examinations for license levels below theirs: Technician. General class licensees may participate as a VE in any exam session, but they may not be the primary VEs administrating the General or Extra class exams. [97.509(b)(3)(i)]

Answer 45

C: You may begin using the General class privileges immediately on receiving your CSCE, but you must append the identifier "temporary AG" or "/AG" to indicate that you passed the General class exam. [97.9(b)]

Answer 46

A: All license exams are administered through the Volunteer Examiner Coordinator (VEC) system. VEs (Volunteer Examiners) must be accredited by a VEC. There must be three VEC-accredited VEs present at every exam session. Technician exams are administered by General class or higher VEs. [97.509(a), 97.509(b)]

Answer 47

D: All license exams are administered through the Volunteer Examiner Coordinator (VEC) system. VEs (Volunteer Examiners) must be accredited by a VEC. There must be three VEC-accredited VEs present at every exam session. Technician exams are administered by General class or higher VEs. As soon as the FCC issues your General class license (meaning that it has appeared in the FCC database) and you receive your accreditation from a VEC, you can participate in exam sessions for Technician license exams. [97.509(b)(3)(i)]

Answer 48

A: You must add a “temporary identifier” to your call sign so that stations receiving your transmissions can verify that you are authorized to transmit on that frequency. If a temporary identifier was not used, between the time you pass your exam and the time at which your new privileges appear in the FCC data base, it would appear that you were transmitting on a frequency for which you were not authorized. When you upgrade to Extra class, you’ll append “temporary AE” to your call sign. [97.119(f)(2)]

Answer 49

C: A Volunteer Examiner Coordinator (VEC) organization is responsible for certifying Volunteer Examiners and evaluating the results of all exam sessions administered by them. VECs also process all of the license application paperwork and submit it to the FCC. [97.509(b)(1)]

Answer 50

B: A VE’s citizenship does not matter, only whether the individual has demonstrated adequate knowledge of the US Amateur Service rules by passing the appropriate license exams. [97.509(b)(3)]

Answer 51

C: Although your new license class should appear in the FCC database within a few days of passing your examination, should there be a delay, remember that the CSCE is only good for 365 days. After that time, you’ll have to re-take the examination! [97.9(b)]

Answer 52

B: 18 years old was determined to be an appropriate age to properly manage an amateur examination session. [97.509(b)(2)]

Answer 53

A: Third-party communication is available to anyone except someone with a revoked amateur license from any country. This prevents someone whose ability to make use of Amateur Radio was taken away from regaining access to amateur frequencies under the guise of third party communications. [97.115(b)(2)]

Answer 54

D: FCC rules allow any holder of an amateur license to be the control operator of a repeater. The control operator of the repeater must have privileges on the frequency on which the repeater is transmitting, however. A 10 meter repeater must have a General class or higher control operator because Technician and Novice licensees don’t have privileges on the 10 meter repeater band. A 10 meter repeater may retransmit the 2 meter signal from a Technician class operator because the 10 meter control operator holds at least a General class license. (Of course the operator transmitting to the repeater must have privileges on the frequency on which he or she is transmitting.)[97.205(a)]

Answer 55

B: Amateur allocations vary between the different ITU regions of the world. FCC Rule 97.301 contains a complete listing of allocations for U.S. hams. Parts (a) and (d) of that section contain the Region 2 frequency allocations that apply to General class amateurs operating from the US. [97.301(d)]

Answer 56

D: Aside from the general requirement to avoid causing harmful interference to other licensed stations and primary service licensees, there are several specific instances in which amateurs must take extra steps to avoid interference. FCC Monitoring Stations require an environment free of strong or spurious signals that can cause interference. The location of monitoring stations can be determined from a regional FCC office. Spread spectrum (SS) transmissions, because of their nature, have the potential to interfere with fixed frequency stations, so SS users should be sure their transmissions will not cause interference. [97.13(b), 97.311(b), 97.303]

Answer 57

C: The FCC and other licensing authorities want to be very sure that the Amateur Service is not abused to provide communications that should properly be conducted through commercial or government services. As a result, third-party communication is restricted to the types of messages in answer C. [97.115(a)(2), 97.117]

Answer 58

A: The FCC considers repeater frequency coordination to be “good engineering and amateur practice.” As such, amateurs are expected to use frequency coordination methods whenever the potential for interference exists. As a consequence, the burden of resolving interference between a coordinated and non-coordinated repeater system falls on the operator of the non-coordinated system. [97.205(c)]

Answer 59

C: The general rule is that third-party traffic with amateurs in any country outside the US is prohibited unless specifically permitted by a third-party agreement between the United States and that country. Don’t assume that it is permitted. Check Table G1-2 which lists countries having third-party agreements with the United States. If the country is not listed, you may not exchange third-party traffic with amateurs operating in that country. [97.115(a)(2)] {br/}{br/}{image src='TableG1-2.png'}

Answer 60

B: The non-licensed person is, by definition, a third-party and any messages you allow them to send or send on their behalf are third-party traffic. The non-licensed person can not have had an amateur license revoked as discussed in question G1E01. [97.115(a), 97.115(b)]

Answer 61

C: Identification by all US-licensed stations when using phone transmissions must be performed in English. [97.119(b)(2)]

Answer 62

D: The only HF authorization for repeater stations is on the 10 meter band between 29.5 and 29.7 MHz. [97.205(b)]

Answer 63

A: Single-sideband (SSB) modulation removes the carrier and one sideband from an AM signal to conserve spectrum and for improved power efficiency. Amateurs normally use the upper sideband for 20 meter phone operation. Whether the upper or lower sideband is used is strictly a matter of convention and not of regulation, except on 60 meters where USB is required. The convention to use the lower sideband on the bands below 9 MHz and the upper sideband on the higher-frequency bands developed from the design requirements of early SSB transmitters. Although modern amateur SSB equipment is more flexible, the convention persists. If everyone else on a particular band is using a certain sideband, you will need to use the same one in order to be able to communicate.

Answer 64

B: Amateurs normally use the lower sideband for 160, 75 and 40 meter phone operation. Whether the upper or lower sideband is used is strictly a matter of convention, and not of regulation, except on 60 meters where USB is required. The convention to use the lower sideband on the bands below 9 MHz and the upper sideband on the higher-frequency bands developed from the design requirements of early SSB transmitters. Although modern amateur SSB equipment is more flexible, the convention persists. If everyone else on a particular band is using a certain sideband, you will need to use the same one in order to be able to communicate.

Answer 65

A: Amateurs normally use the upper sideband for VHF and UHF phone operation. Whether the upper or lower sideband is used is strictly a matter of convention, and not of regulation, except on 60 meters where USB is required. The convention to use the lower sideband on the bands below 9 MHz and the upper sideband on the higher-frequency bands developed from the design requirements of early SSB transmitters. Although modern amateur SSB equipment is more flexible, the convention persists. If everyone else on a particular band is using a certain sideband, you will need to use the same one in order to be able to communicate.

Answer 66

A: Amateurs normally use the upper sideband for 17 and 12 meter phone operation. Whether the upper or lower sideband is used is strictly a matter of convention, and not of regulation, except on 60 meters where USB is required. The convention to use the lower sideband on the bands below 9 MHz and the upper sideband on the higher-frequency bands developed from the design requirements of early SSB transmitters. Although modern amateur SSB equipment is more flexible, the convention persists. If everyone else on a particular band is using a certain sideband, you will need to use the same one in order to be able to communicate.

Answer 67

C: Most amateurs who use voice communications on the high frequency bands use single sideband (SSB) voice. There are some operators who prefer the high-fidelity audio of double-sideband full-carrier amplitude modulation (AM). AM requires more than twice the bandwidth of an SSB signal, however. There is also some frequency modulated (FM) and phase modulated (PM) voice operation on the 10 meter band, but that mode also requires a much wider bandwidth than SSB. Some amateurs are beginning to experiment with digitally encoded voice communications, but SSB is the most common HF voice mode.

Answer 68

B: Single sideband (SSB) voice communication is used much more frequently than other voice modes on the HF bands because it uses less spectrum space. The RF carrier is not transmitted with an SSB signal. That means SSB transmissions are more power efficient, since the full transmitter power can be used to transmit the one sideband rather than being divided between the two sidebands and the carrier as it would be for AM.

Answer 69

B: Single sideband (SSB) voice transmissions are identified by which sideband is used. If the sideband with a frequency lower than the RF carrier frequency is used, then the signal is known as a lower sideband (LSB) transmission. If the sideband with a frequency higher than the RF carrier frequency is used, then the signal is known as an upper sideband (USB) transmission. In both cases the opposite sideband is suppressed. Amateurs normally use lower sideband on the 160, 75/80 and 40 meter bands, and upper sideband on the 20, 17, 15, 12 and 10 meter bands. This is not a requirement of the FCC Rules in Part 97, though. It is simply by common agreement. FCC Rules do, however, require amateurs to use USB on the five channels of the 60 meter band.

Answer 70

B: To break into a conversation, you will have to wait until both stations are listening so that your signal will be heard. In order that your transmissions be identified during this brief period, simply state your call sign. No “over” or “break” is required, nor do you have to give either of the transmitting station’s call signs.

Answer 71

D: Whether the upper or lower sideband is used is strictly a matter of convention, and not of regulation, except on 60 meters where USB is required. The convention to use the lower sideband on the bands below 9 MHz and the upper sideband on the higher-frequency bands developed from the design requirements of early SSB transmitters. Although modern amateur SSB equipment is more flexible, the convention persists. If everyone else on a particular band is using a certain sideband, you will need to use the same one in order to be able to communicate.

Answer 72

B: The purpose of a voice operated transmit (VOX) circuit is to provide automatic transmit/receive (TR) switching within an amateur station. By simply speaking into the microphone, the antenna is connected to transmitter, the receiver is muted and the transmitter is activated. When you stop speaking, the VOX circuit switches everything back to receive. Using VOX allows hands-free operation.

Answer 73

C: DX means “distant stations” in ham jargon, so combining CQ which means “I am calling any station” with DX means “I am calling any distant station.” You may also hear stations making targeted calls by combining CQ with some other description, such as “CQ mobile stations" or “CQ California.” It is polite to avoid responding if you are not of the type of station being called.

Answer 74

C: Except when the FCC has declared there to be a communications emergency and designated specific frequencies for emergency communications, no single or group of amateurs has priority on any amateur frequency. Good operating practice is to use the flexibility of the amateur service to avoid interference and minimize any interference from your operation.

Answer 75

B: Whenever you hear a station in distress (where there is immediate threat to human life or property), you should take whatever action is necessary to determine what assistance that station needs and attempt to provide it. Don’t assume that some other station will handle the emergency; you may be the only station receiving the distress signal. If you do hear a station in distress, the first thing you should do is to acknowledge that you heard the station, and then ask the operator where they are located and what assistance they need.

Answer 76

C: Good operating practice suggests that whoever can most easily resolve an interference problem be the one to do so. If you begin to have interference from other activity on the same frequency, moving your contact to another frequency may be the simplest thing to do. Switching antennas or rotating a beam antenna may also achieve the same results.

Answer 77

B: The more bandwidth occupied by a signal, the more frequency separation you will need from a contact currently in progress to avoid interference. CW emissions require the least bandwidth and need the least frequency separation. Most radios use narrow filters for CW reception, so you should be able to select an operating frequency within about 150 to 500 Hz from another CW station without causing interference.

Answer 78

B: The more bandwidth occupied by a signal, the more frequency separation you will need from a contact currently in progress to avoid interference. Single-sideband (SSB) signals require considerably more bandwidth than CW and therefore much more frequency separation between contacts. You will need approximately 3 kHz of separation from another contact under normal conditions to avoid causing interference.

Answer 79

A: After listening for a short period of time, if you do not hear another station transmitting on the frequency, it is good practice to make a short transmission asking if the frequency is in use. It may be that due to propagation you are unable to hear the transmitting station, but the listening station can hear you. On CQ, the Q-signal "QRL?", and on phone, "Is the frequency in use?" followed by your call sign give the opportunity for another station to respond.

Answer 80

C: Under normal conditions, following the voluntary band plan in Table G2B07 is a good way to choose a frequency compatible with your planned type of operating. Very crowded bands or special operating events require that you be flexible in your frequency choices. {br/}{br/}{image src='TabG2B07.png'}

Answer 81

A: Outside the United States, particularly in ITU Regions 1 and 3, amateurs share the 160 and 80 meter band with government and commercial stations. They may have very limited allocations, as well. The DX window is a section of the band where these stations may be contacted without their having to compete with stronger domestic signals. DX windows are also generally used only for contacts with stations outside the contiguous United States and Canada.

Answer 82

A: The control operator of a RACES station must have an FCC-issued amateur operator license and be certified by a civil defense organization as a member. [97.407(a)]

Answer 83

D: If the War Emergency Powers have been activated, RACES stations are restricted to operations in the frequency ranges listed in §97.407(b). [97.407(b)]

Answer 84

A: When normal communications are not available and the immediate safety of human life or protection of property is involved, all of the normal rules for an amateur station are suspended so that you can obtain assistance. This means that any method of communication, on any frequency, and at any power output, may be used to communicate and resolve the emergency. It doesn’t matter if the distress is personal to the station or a general disaster. Just be sure you have a real emergency![97.405]

Answer 85

C: No FCC rule prevents an amateur station from using any means of radiocommunications at its disposal to assist a station in distress. [97.405(b)]

Answer 86

D: Full break-in telegraphy allows you to receive signals between your transmitted Morse code dots and dashes and between words. The advantage is that if you are sending a long message, the receiving station can send back to you (break in) and stop you for repeats of missed words. QSK is the Q signal used to describe this type of operation.

Answer 87

A: QRS is the Q-signal that means “Send slower”. To ask if you should send slower, send QRS? Conversely, to increase speed, QRQ is used.

Answer 88

C: KN is an example of a CW prosign, procedural signals that help coordinate the exchange of messages and the beginning and ending of transmissions. The patterns of dots and dashes that make up prosigns are described by a pair of regular letters that, if sent together without a pause, are equivalent to the prosign. (Prosigns are often written with a line over the letters to indicate they are sent with no spaces between them as a single character.)

Answer 89

D: CL is an example of a CW prosign, procedural signals that help coordinate the exchange of messages and the beginning and ending of transmissions. The patterns of dots and dashes that make up prosigns are described by a pair of regular letters that, if sent together without a pause, are equivalent to the prosign. (Prosigns are often written with a line over the letters to indicate they are sent with no spaces between them as a single character.)

Answer 90

B: An operator calling CQ is assumed to be sending at a speed at which he or she feels comfortable receiving. Responding at a significantly higher speed is impolite and may be embarrassing to the other operator if they are unable to copy your response. If you are uncomfortable responding at the sending station’s speed, send at the highest rate at which you are comfortable receiving. It is good practice to respond to calling stations at their sending speed, if it is significantly slower.

Answer 91

D: Zero beat means to match the frequency of the transmitting station. When separate receivers and transmitters were the norm, a transmitter’s frequency had to be adjusted to match the received signal’s frequency. This was done by spotting -- turning on the transmitter’s low power stages and listening for that signal in the receiver. When the beat frequency between the desired signal and the transmitter’s spotting signal reached zero frequency or zero beat, the transmitter signal and the received signal were on matching frequencies.

Answer 92

A: An RST with “C” appended, such as 579C, indicates that the signal is being received with chirp, a short frequency shift as the transmitter stabilizes after keying. It’s a very distinctive sound and is caused by the transmitter’s oscillator changing frequency when the key is closed. This can be due to oscillator circuit design or poor regulation of the transmitter power supply.

Answer 93

C: The ARRL National Traffic System has established specific procedures for passing formal written messages by Amateur Radio. Even if you don’t participate in traffic nets, it is a good idea to be familiar with the procedures for handling such messages. It can be especially helpful in an emergency for a number of reasons. By following the standard procedures it is more likely that an emergency message will be transmitted (and received) correctly. When sending formal messages using Morse code (CW), you send the message preamble, the address, message body and signature. To indicate that this is the end of the message, send the CW procedural signal (prosign) “AR” to show clearly that all the information has been sent. When the receiving station has accurately recorded the entire message, they will acknowledge receipt of the message by sending “QSL” or simply “R” for “received.”

Answer 94

C: QSL is the Q-signal that means “I acknowledge receipt”. Informally, it is often used to indicate that a transmission was received and understood. QSL cards are exchanged to confirm that a contact was made.

Answer 95

B: QRQ is the Q-signal that means “Send faster." To ask if you should send faster, send QRQ? Conversely, to decrease speed, QRS is used.

Answer 96

D: QRV is the Q-signal that means “I am ready to copy” and indicates that the station with the message may begin transmitting. QRV is used whether the message is formal traffic or just regular conversation.

Answer 97

A: The purpose of the Amateur Auxiliary is to help ensure amateur self-regulation and see that amateurs follow the FCC rules properly. The Amateur Auxiliary volunteers deal only with amateur-to-amateur interference and improper operation. The other answer choices describe other Amateur Radio activities. Amateur volunteers who conduct licensing examinations are called Volunteer Examiners (VEs). Amateurs in charge of frequency coordination for repeaters are called Frequency Coordinators. Amateurs who help civil defense organizations in times of emergency are members of the Radio Amateur Civil Emergency Service (RACES).

Answer 98

B: The purpose of the Amateur Auxiliary is to help ensure amateur self-regulation and see that amateurs follow the FCC rules properly. The Amateur Auxiliary volunteers deal only with amateur-to-amateur interference and improper operation. The other answer choices describe other Amateur Radio activities. Amateur volunteers who conduct licensing examinations are called Volunteer Examiners (VEs). Amateurs in charge of frequency coordination for repeaters are called Frequency Coordinators. Amateurs who help civil defense organizations in times of emergency are members of the Radio Amateur Civil Emergency Service (RACES). Many amateurs also volunteer to help provide emergency and public safety communications as members of ARRL’s Amateur Radio Emergency Service (ARES).

Answer 99

B: Friendly competitions to locate hidden transmitters, sometimes called "fox hunts" or "bunny hunts", allow participants to practice their radio direction-finding skills which are useful in locating harmful interference sources. The Amateur Auxiliary can use "Fox Hunters" to document interference cases and report them to the proper enforcement bureau. Fox hunts also make everyone aware that there is a plan in place to find and eliminate an interference source.

Answer 100

B: An azimuthal map, or azimuthal-equidistant projection map, is also called a great circle map. When this type of map is centered on your location, a straight line is equivalent to stretching a string between two points on a globe, and will give you the shortest distance between two points. This type of map is used for determining the direction to point your antenna for short-path communications. (A compass bearing 180 degrees different from the short-path direction will indicate the direction to point your antenna for long-path communications.) {br/}{br/}{image src='Fig G2-01.png'}

Answer 101

B: U.S. amateurs are permitted to contact amateurs in any other country. There have been a very few instances in which a government has prohibited contact between its amateurs and those of a particular country. [97.111(a)(1)]

Answer 102

C: The shortest direct route, or great-circle path between two points, is called the short-path. If a directional antenna is pointed in exactly the opposite direction, 180 degrees different from the short-path direction, communications can be attempted on the long-path. Long-path communication may be available when the more direct short path is closed. Because of the higher number of hops required, long path often works best when the path is across the ocean, a good reflector of HF signals. {br/}{br/}{image src='Fig G2-02.png'}

Answer 103

A: The FCC Rules for operating on the amateur 60 meter band are quite different from the rules for any other amateur band. One significant difference is the requirement to transmit with no more than 50 watts effective radiated power (ERP). ERP is a measurement of power as compared to that radiated from a dipole. If you are using a half-wavelength dipole antenna, you can use up to 50 W PEP from your transmitter on that band. If you are using an antenna that has some gain compared to a dipole, then you will have to reduce your transmitter power accordingly. If the antenna has a gain of 3 dBd (3 dB compared to a dipole) then you would have to reduce transmitter power by half (to 25 W PEP). The FCC requires you to keep a record of your antenna gain, if it is more than a dipole. This record can either be from the manufacturer’s data, from calculations of the gain or from gain measurements. [97.303(s)]

Answer 104

D: While useful, the FCC does not require you to keep a record (log) of your transmissions. It can be fun to keep a log, though, and then look back years later at the contacts you made. A log can also help document when your station was on the air and who was the control operator. You must give permission before a visiting amateur may operate your station. If you designate another amateur to be the control operator of your station, you both share the responsibility for the proper operation of the station. Unless your station records (log) show otherwise, the FCC will assume you were the control operator any time your station was operated as stated in FCC rule 97.103(b).

Answer 105

D: You can keep any information in your log that you would like to remember later. At a minimum, most amateurs keep a record of the date and time of each contact as well as the frequency or band of the contact. The station call sign, mode, and the RST signal report given and received are also normally recorded. Many amateurs also record the name of the other operator as well as his or her location.

Answer 106

B: QRP is a Q signal that means “lower your transmitter power.” Many amateurs enjoy using low power levels for the challenge, the relative simplicity of the equipment, and sometimes to reduce interference. The generally accepted level for “QRP” power is 5 watts of transmitter output on CW and 10 W PEP output on phone.

Answer 107

C: Most of the time we think about using a beam antenna to send more of our transmitted power toward the desired station. A beam antenna can also be an effective tool for fighting received interference. For example, you might be having a conversation with another amateur but a strong signal from another station on a nearby frequency is causing a bit of interference. With a beam antenna you might be able to turn the antenna so the interfering station is off the side or back of your antenna. In that case the antenna will not receive as strong a signal from the interfering station. Ideally, you would have an antenna that sends and receives signals in only one direction, rejecting signals in all other directions. This is called a unidirectional antenna. Most Yagi antennas send and receive some signal off the back and sides of the antenna but it is significantly less than the amount that is sent and received from the front.

Answer 108

D: Lower sideband (LSB) is used by convention for RTTY signals on all bands. There is no technical reason why LSB is preferred over USB for RTTY signals.

Answer 109

A: One of the interesting properties of the PSK31 radioteletype mode is that it uses a character code called Varicode. Developed by Peter Martinez, G3PLX, Varicode uses shorter character lengths for the more common characters and longer codes for less common characters. (Morse code also uses variable length characters.) Thus, the number of data bits per character depends on which character is being sent. This is quite different from other digital modes that use fixed-length codes. For example, all RTTY Baudot code characters have five data bits.

Answer 110

C: Packet radio gets its name from the concept of breaking the information to be transmitted into small pieces, called packets. Each packet can be transmitted and make its way through the network independently. The entire message is then reassembled at the receiving station. Each packet begins with a header that contains several sets (fields) of information about the packet. The address field of the header contains information about the station for which the message is intended, the sending station and possibly specific relay stations. A control field contains information about the type of data being sent. A frame number allows the receiving station reassemble the entire message in order. The data field of the packet contains the actual data being sent. After the data field there is a frame check sequence (FCS) or cyclic redundancy check (CRC) field that is used for error detection.

Answer 111

B: The FCC’s rules specify where RTTY and data transmissions allowed, but the band plans tell you where such signals are usually found. The band plan in Table G2E04 calls for RTTY and data operation from 14.070 to 14.100 MHz on 20 meters. {br/}{br/}{image src='Table G2E04.png'}

Answer 112

C: The Baudot code used for radioteletype (RTTY) has five data bits per character. This means there are only 32 possible character combinations. The code only transmits upper case letters. “LTRS” and “FIGS” characters select the alphabet table or a numbers and punctuation table to provide additional characters. RTTY is an asynchronous communications mode, so each character must also include a start and a stop bit.

Answer 113

B: RTTY operation on the HF bands uses frequency-shift keying (FSK) to convey the information. The transmitted signal shifts between two frequencies, called the MARK and SPACE frequencies. The two frequencies used are normally 170 Hz apart for HF communications.

Answer 114

B: RTTY stands for radioteletype. The FCC’s name for RTTY emissions is narrow-band, direct printing telegraphy.

Answer 115

A: The FCC’s rules specify where RTTY and data transmissions allowed, but the band plans tell you where such signals are usually found. Table G2E04 gives the band plan calls for RTTY operation as from 3570 to 3600 kHz on 80 meters. {br/}{br/}{image src='Table G2E04.png'}

Answer 116

D: PSK signals are generally found in the vicinity of 14.070 MHz on the 20 meter band at the bottom of the RTTY area listed in Table G2E04. {br/}{br/}{image src='Table G2E04.png'}

Answer 117

D: MFSK16 stands for Multi-Frequency Shift Keying with 16 different tones being transmitted. On the air, an MFSK16 signals sounds like a set of whistles all being played simultaneously in a narrow bandwidth. By carefully shaping the signal and controlling how the tones are turned on and off, MFSK16 modulation is able to better withstand the fading and distortion associated with sky-wave signals.

Answer 118

B: MFSK16 stands for Multi-Frequency Shift Keying with 16 different tones being transmitted. On the air, an MFSK16 signals sounds like a set of whistles all being played simultaneously in a narrow bandwidth. By carefully shaping the signal and controlling how the tones are turned on and off, MFSK16 modulation is able to better withstand the fading and distortion associated with sky-wave signals.

Answer 119

B: ARQ stands for Automatic Repeat Request. In an ARQ digital mode, if a transmitted packet is received with errors, the receiving station may request a re-transmission of the packet automatically.

Answer 120

A: PACTOR is an ARQ (Automatic Repeat Request) digital mode in which the receiving station sends a response to the transmitting station indicating whether the data was received correctly or not. An ACK (Acknowledge) response means the data was received correctly. A NAK (Not Acknowledge) response means that errors were detected in the received data.

Answer 121

A: A number of observatories around the world measure solar activity. A weighted average of this data is used to determine the International Sunspot Number (ISN) for each day. These daily sunspot counts are used to produce monthly and yearly average values. The average values are used to see trends and patterns in the measurements. {br/}{br/}{image src='Fig G3-02.png'}

Answer 122

B: A sudden ionospheric disturbance (SID) is often the result of solar flares that release large amounts of radiation. Ultraviolet and X-ray radiation from the Sun travels at the speed of light, reaching the Earth in about eight minutes. When this radiation reaches the Earth, the level of ionization in the ionosphere increases rapidly. This causes D-layer absorption of radio waves to increase significantly. Absorption of radio signals in the D-layer is always stronger at lower frequencies, affecting lower frequency signals more than higher frequency signals. {br/}{br/}{image src='Fig G3-02.png'}

Answer 123

C: Ultraviolet and X-ray radiation from the Sun travels at the speed of light, reaching the Earth in about eight minutes.

Answer 124

D: The higher the frequency, the more ionization is needed in the ionosphere in order to refract (bend) the radio signal back to the Earth. When solar activity is low, the higher frequencies will pass through the ionosphere into space instead of being refracted back to Earth. During periods of low solar activity, the 15 meter (21 MHz), 12 meter (24.9 MHz) and 10 meter (28 MHz) bands are the least reliable HF bands for long distance communication.

Answer 125

D: Solar flux is the radio energy coming from the Sun. High levels of solar energy produce greater ionization in the ionosphere. The solar flux measurement is taken daily by measuring radio energy from the Sun at 2800 MHz which is a wavelength of 10.7 cm. The measurement is then converted into the solar flux index. Higher values of the solar flux index correspond to higher values of solar flux. The solar-flux measurement may be taken under any weather conditions--the Sun does not have to be visible, as for determining the sunspot number. The radio energy measurement is converted to an open-ended numeric index with a minimum value of 65 (for the minimum amount of energy). Higher values of the solar flux index indicate higher levels of solar activity.

Answer 126

D: Geomagnetic disturbances result when charged particles from a solar flare reach the Earth. When these charged particles reach the Earth’s magnetic field, they are deflected toward the North and South poles. Radio communications along higher-latitude paths (latitudes greater than about 45 degrees) will be more affected than paths closer to the equator. The charged particles from the Sun may make the F-region seem to disappear or seem to split into many layers, degrading or completely blacking out long-distance radio communications.

Answer 127

D: Even at the minimum point of the solar cycle, world-wide propagation is usually possible on the 20 meter band. As solar activity increases, the band will remain open for longer periods and with stronger signal strengths. For this reason, 20 meters is a favorite band for “DXers".

Answer 128

B: Geomagnetic disturbances result when charged particles from a solar flare reach the Earth. When these charged particles reach the Earth’s magnetic field, they are deflected toward the North and South poles. Radio communications along higher-latitude paths (latitudes greater than about 45 degrees) will be more affected than paths closer to the equator. The charged particles from the Sun may make the F-region seem to disappear or seem to split into many layers, degrading or completely blacking out long-distance radio communications.

Answer 129

C: When sunspot numbers are high, there is a significant amount of solar activity and there will be more ionization of the ionosphere. The more the ionosphere is ionized, the higher the frequency of radio signals that may be used for long-distance communication. During the peak of a sunspot cycle, the 20 meter (14 MHz) band will be open around the world even through the night. During an unusually good sunspot cycle, even the 6 meter (50 MHz) band can become usable for long-distance communication.

Answer 130

C: It takes approximately 28 days for the Sun to rotate on its axis. Since active areas on the Sun may persist for more than one rotation, you can expect good propagation conditions to recur approximately every 28 days.

Answer 131

D: The internal dynamics of the Sun cause its activity to vary in a cycle lasting approximately 11 years. Sunspots are one indication of solar activity and since they were the earliest phenomenon observed on the Sun, the cycle is called the sunspot cycle.

Answer 132

B: The K-index represents readings of the Earth’s geomagnetic field, updated every three hours at Boulder, Colorado. K-index values indicate the stability of the Earth’s geomagnetic field. Steady values indicate a stable geomagnetic field, while rising values indicate an active geomagnetic field. The K-index trends are important indicators of changing propagation conditions. Rising K-index values are generally bad news for HF propagation, especially for propagation paths involving latitudes above 30° north. Values of 4 and rising warn of conditions associated with auroras and degraded HF propagation.

Answer 133

C: The A-index is a daily figure for the state of activity of the Earth’s magnetic field. The A-index tells you mainly about yesterday’s conditions, but it is very revealing when charted regularly, because geomagnetic disturbances nearly always recur at four-week intervals. (It takes the Sun 28 days to rotate once on its axis.)

Answer 134

B: The corona is the Sun’s outer layer. Temperatures in the corona are typically about two million degrees Celsius, but can be more than four million degrees Celsius above an active sunspot region. A coronal hole is an area of somewhat lower temperature. Matter ejected through such a “hole” is in the form of plasma, a highly ionized gas made up of electrons, protons and neutral particles. The plasma travels at speeds up to two million miles per hour, and if the “jet” of material is directed toward the Earth it can result in a geomagnetic storm on Earth, disrupting HF communications.

Answer 135

D: The corona is the Sun’s outer layer. Temperatures in the corona are typically about two million degrees Celsius, but can be more than four million degrees Celsius above an active sunspot region. Matter ejected from the corona is in the form of plasma, a highly ionized gas made up of electrons, protons and neutral particles. The plasma travels at speeds of two million miles per hour or more, so it can take about 20 to 40 hours for the plasma to travel the 93 million miles to Earth.

Answer 136

A: When the plasma, or charged particles, from a coronal mass ejection reaches the Earth it interacts with the Earth’s magnetic field. The charged particles follow magnetic field lines into the Earth’s atmosphere near the North and South magnetic poles, producing visible aurora borealis at northern latitudes and aurora australis in the south. VHF operators look forward to such conditions because radio signals can be reflected from auroral “patches,” making long-distance contacts possible.

Answer 137

D: Normally, you will expect radio signals to arrive at your station by following the shortest possible path between you and the transmitting station. This is called short-path propagation. Signals that might have arrived from the opposite direction, 180 degrees different from the short-path signals are normally so weak that you would probably not hear them. Signals that arrive 180 degrees from the short path are called long-path signals. When propagation conditions are suitable, the long-path signals may be strong enough to support communication. In fact, there are times when the long-path propagation may be even better than the short-path propagation. Stations with directional antennas can point their antennas directly away from each other to communicate. (This is not simply communicating using signal radiated “off the back” of the antennas.) If you are listening to signals on your receiver and you hear a well-defined echo, even if it is a weak echo, the chances are you are hearing signals arrive at your station over the long path. The slightly longer time it takes the signals to travel the longer distance around the Earth results in a slight delay when compared to the direct, short-path signals. This is a good indication that you may be able to point your antenna directly away from the received station to communicate.

Answer 138

A: As the maximum usable frequency (MUF) for a given path increases, the ionosphere also supports shorter single-hop distance at lower frequencies. Suppose you are operating on the 10 meter band, and are contacting stations that are 800 to 1000 miles away. After making a few more contacts you start to notice that you are contacting stations only about 500 miles away, and then you notice that you are contacting stations even closer, perhaps only out to a few hundred miles. This can be an excellent indication that the MUF for the longer-path stations has moved up to a higher frequency, perhaps even above 50 MHz. It is a good time to check for a band opening on 6 meters!

Answer 139

A: Ionospheric absorption (attenuation) is lowest just below the Maximum Usable Frequency (MUF), the highest frequency that will allow the radio wave to reach its desired destination using E or F-region propagation. Use a frequency just below the MUF for the highest received signal strength.

Answer 140

A: Beacon stations transmit signals so that amateur operators can evaluate propagation conditions. By listening for beacon stations from Western Europe, you will be able to determine if the MUF is high enough for 10 meter communications to that area.

Answer 141

A: The Maximum Usable Frequency (MUF) and Lowest Useable Freuqency (LUF) relate to a particular desired destination. The MUF is the highest frequency that will allow the radio wave to reach its desired destination using E or F-region propagation. The LUF is the lowest frequency at which ionospheric absorption is low enough to allow a signal to reach the desired destination. There is no single MUF or LUF for a given transmitter location; it will vary depending on the direction and distance to the station you are attempting to contact. Signals with frequencies above the LUF and lower than the MUF are generally bent back to Earth and at frequencies higher than the MUF will pass through the ionosphere instead of being bent back to the Earth. {br/}{br/}{image src='Fig G3-03.png'}

Answer 142

C: The Lowest Usable Frequency (LUF) is the frequency below which ionospheric absorption attenuates the radio signals to below the atmospheric noise levels. Since absorption increases with decreasing frequency, signals at frequencies below the LUF can not be received via sky-wave communication.

Answer 143

A: The Lowest Usable Frequency (LUF) is the frequency below which ionospheric absorption attenuates the radio signals to below the atmospheric noise levels. Since absorption increases with decreasing frequency, signals at frequencies below the LUF can not be received via sky-wave communication.

Answer 144

B: The Maximum Usable Frequency (MUF) relates to a particular desired destination. The MUF is the highest frequency that will allow the radio wave to reach its desired destination using E or F-region propagation. There is no single MUF for a given transmitter location; it will vary depending on the direction and distance to the station you are attempting to contact. Signals with frequencies lower than the MUF are generally bent back to Earth and at higher than the MUF will pass through the ionosphere instead of being bent back to the Earth.

Answer 145

C: Layers in the F region form and decay in correlation with the daily passage of the sun. The F1 and F2 layers form when the F region splits into two parts due to high radiation from the Sun, recombining into a single F layer at night. The more solar radiation the F region receives, the more it is ionized so it reaches maximum ionization shortly after noon during the summertime. The ionization tapers off very gradually towards sunset and the F2 layer remains usable into the night. The F2 region is the highest of the ionosphere, reaching as high as 300 miles at noon in the summertime. Because it is the highest, it is the region mainly responsible for long-distance communications. A one-hop transmission can travel a maximum distance of about 2,500 miles using F2 propagation. {br/}{br/}{image src='Fig G3-04.png'}

Answer 146

B: The E region of the ionosphere is the second lowest, just above the D region. The E layer forms at an altitude of about 70 miles above the Earth. The E region ionizes during the daytime, but does not stay ionized very long after sunset. Ionization in the E region is at a maximum around midday. During the daytime, a radio signal can travel a maximum distance of about 1,200 miles in one hop using E-region propagation. {br/}{br/}{image src='Fig G3-04.png'}

Answer 147

A: Signals at frequencies below the LUF will be absorbed in the ionosphere rather than returning to Earth. Occasionally the LUF may be higher than the maximum usable frequency (MUF). This means that for the highest possible frequency that will propagate through the ionosphere for that path, the signal absorption is so large that even signals at the MUF are absorbed. Under these conditions it is impossible to establish sky-wave communication between those two points no matter what frequency is used! (Communications between either location and other locations may be possible, since the LUF and MUF depend on the end points of the communication path.)

Answer 148

D: The Maximum Usable Frequency (MUF) is the highest frequency that will provide sky-wave propagation between two specific locations. For example, suppose you live in Illinois and want to communicate with another amateur in Ecuador. You might find that the MUF for this contact is about 18 MHz at 14:00 UTC. You may also find that the MUF to communicate with a station in Spain at that same time is 12 MHz. Different communications path distances and directions will often result in very different MUF values. The MUF depends on conditions in the ionosphere, and those conditions will vary by time of day as well as the season of the year. The amount of solar radiation striking the ionosphere varies significantly depending on the timing of the 11-year sunspot cycle. Any solar flares, coronal-mass ejections and other disturbances on the Sun can also result in ionospheric disturbances that will affect the MUF. Answer choices A, B and C all describe factors that will affect the MUF for a given sky-wave propagation path, so answer choice D is correct.

Answer 149

A: The D region of the ionosphere is the lowest, forming the D layer at a height of 30 to 60 miles. Because it is the lowest, it is also the densest and its ionization disappears by dark. {br/}{br/}{image src='Fig G3-05.png'}

Answer 150

A: The F region forms and decays in correlation with the daily passage of the Sun. The F1 and F2 layers form when the F region splits into two parts due to receiving high radiation from the Sun, recombining into a single F region at night. The more solar radiation the F region receives, the more it is ionized so it reaches maximum ionization shortly after noon during the summertime. The ionization tapers off very gradually towards sunset and the F2 region remains usable into the night. The F2 region is the highest of the ionosphere, reaching as high as 300 miles at noon in the summertime. {br/}{br/}{image src='Fig G3-05.png'}

Answer 151

C: Because the F2 region is the highest ionospheric region, it is the region mainly responsible for long-distance communications. A one-hop transmission can travel a maximum distance of about 2500 miles using the F2 region. {br/}{br/}{image src='Fig G3-04.png'}

Answer 152

D: At each frequency there is a maximum angle at which the radio wave can leave the antenna and still be refracted back to Earth by the ionosphere instead of simply passing through it and proceeding out into space. The critical angle changes depending on the ionization of the ionosphere. {br/}{br/}{image src='Fig G3-06.png'}

Answer 153

C: Think of the D region as the "Darned Daylight" region. Instead of bending high frequency signals back to Earth, it absorbs energy from them. Signals at lower frequencies (longer wavelengths such as 160, 80, 60 and 40 meters) are absorbed more than at higher frequencies. The ionization created by the sunlight does not last very long in the D region, disappearing by sunset. {br/}{br/}{image src='Fig G3-07.png'}

Answer 154

B: The area between the farthest reach of ground-wave propagation and the point where signals are refracted back from the ionosphere (sky-wave propagation) is called the skip zone. Since some of the transmitted signal is scattered in the atmosphere or from ground reflections, communication may be possible in the skip zone by the use of scatter signals. The amount of signal scattered in the atmosphere will be quite small and the signal received in the skip zone will arrive from several radio-wave paths. This tends to produce a weak, distorted signal with a fluttering or wavering sound. {br/}{br/}{image src='Fig G3-08.png'}

Answer 155

D: The amount of signal scattered back towards the transmitting station from the ionosphere or ground will be quite small. The signal received in the skip zone will also arrive from several radio-wave paths. This tends to produce a weak, distorted signal with a fluttering or wavering sound. {br/}{br/}{image src='Fig G3-08.png'}

Answer 156

A: The amount of signal scattered back towards the transmitting station from the ionosphere or ground will be quite small. The signal received in the skip zone will also arrive from several radio-wave paths. This tends to produce a weak, distorted signal with a fluttering or wavering sound. {br/}{br/}{image src='Fig G3-08.png'}

Answer 157

B: The area between the farthest reach of ground-wave propagation and the point where signals are refracted back from the ionosphere (sky-wave propagation) is called the skip zone. Since some of the transmitted signal is scattered in the atmosphere, communication may be possible in the skip zone by the use of scatter signals. {br/}{br/}{image src='Fig G3-08.png'}

Answer 158

D: Frequencies above the Maximum Usable Frequency (MUF) normally pass through the ionosphere out into space rather than being bent back, although atmospheric scatter from the ionosphere will sometimes allow communication on these frequencies. Amateurs trying to communicate on frequencies that seem to be above the MUF may notice that they can communicate using these scattered signals. Had they been using a frequency below the MUF they may not have noticed any scattered signals. {br/}{br/}{image src='Fig G3-08.png'}

Answer 159

B: Low horizontal antennas, such as dipoles between 1/8 and ¼-wavelength above the ground work best for daytime skip communications on low frequencies. Signals from such antennas are radiated at high vertical angles that can be reflected by the ionosphere, but have a minimum amount of attenuation from the D and E layers.

Answer 160

D: Think of the D region as the "Darned Daylight" region. Instead of bending high frequency signals back to Earth, it absorbs energy from them. Signals at lower frequencies (longer wavelengths such as 160, 80, 60 and 40 meters) are absorbed more than at higher frequencies. The ionization created by the sunlight does not last very long in the D region, disappearing by sunset. {br/}{br/}{image src='Fig G3-07.png'}

Answer 161

B: Near Vertical Incidence Sky-wave (NVIS) propagation refers to communication using sky-wave signals transmitted at very high vertical angles. The frequencies used are below the critical frequency, meaning that their critical angle (see question G3C04) is ninety degrees, meaning they can be reflected straight back down to Earth. Because the signals travel at high angles, they have a minimum amount of attenuation from the D and E layers. The result is good communications in a region around the transmitter over distances higher than supported by ground-wave propagation {br/}{br/}{image src='Fig G3-09.png'}

Answer 162

B: A notch filter removes a very narrow band of frequencies - the "notch" - from its input. This allows the notch filter to get rid of an interfering tone, such as from an unmodulated carrier, while maintaining the intelligibility of the desired signal. An automatic notch filter can detect tones and remove them without operator intervention.

Answer 163

C: Interference from nearby signals can often be avoided by moving the receiver's carrier frequency to the "other side" of the desired signal, without changing its audio pitch. This won't work on SSB because it also inverts the spectrum of the speech, rendering it unintelligible.

Answer 164

C: Operating split means using one VFO for transmitting and another for receiving. This is often used when a rare DX station is on the air with many callers. Operating simplex – transmitting and receiving on the same frequency – can result in a lot of confusion with stations trying to hear the DX station while others transmit. By transmitting on one frequency and having callers transmit somewhere else (usually on adjacent frequencies) everyone can hear the DX station and keep “in sync” for more orderly, effective operating.

Answer 165

B: The Tune control of a vacuum tube RF amplifier--either of a standalone amplifier or of a transmitter output stage--adjusts the impedance matching circuit at the frequency of operation. Adjusting the Tune control for a pronounced “dip” in plate current indicates that the circuit is set for the right frequency. The Load or Coupling control is then used to adjust the amount of output power. The Tune and Load controls are alternately adjusted until the required amount of output power is obtained without exceeding the tube’s plate current rating.

Answer 166

C: The ALC circuit of an amplifier senses the amount of input power and generates a feedback voltage to keep a driver stage or transmitter from generating too much power for linear operation. This helps prevent distortion in the amplifier that would cause spurious emissions and interference to other stations.

Answer 167

C: There are many names for devices that use LC circuits to convert one impedance to another; antenna coupler, impedance matching unit, transmatch, and antenna tuner are common.

Answer 168

D: Transistors are more sensitive to input drive levels than the more rugged vacuum tubes and can be damaged very quickly if too much power is applied. Fast-acting control circuits are required to protect the transistors from excessive drive.

Answer 169

D: The Tune control of a vacuum tube RF amplifier--either of a standalone amplifier or of a transmitter output stage--adjusts the impedance matching circuit at the frequency of operation. Adjusting the Tune control for a pronounced “dip” in plate current indicates that the circuit is set for the right frequency. The Load or Coupling control is then used to adjust the amount of output power. The Tune and Load controls are alternately adjusted until the required amount of output power is obtained without exceeding the tube’s plate current rating.

Answer 170

C: If a relay switches while RF is present in the circuit, that is called “hot switching”. At high power levels hot switching can damage the relay and so it is important to let the relay complete switching before energizing the circuit. Similarly, it is important to disconnect sensitive receive circuits before transmitter RF is enabled. A controlled time -delay, called “sequencing” is used to ensure that all relay and switching operations are completed before enabling the transmitter.

Answer 171

B: Electronic keyers eliminate a lot of the manual work involved in operating a straight key and insure that each dot or dash has the right length and spacing. This allows comfortable high-speed Morse operation even for extended periods of time.

Answer 172

A: Passband or IF shift adjusts the receiver’s passband above or below the displayed carrier frequency to avoid interfering signals. This results in a shift in tone of the received signal, but often improves intelligibility.

Answer 173

C: Dual VFOs are used for split operation. Operating split means using one VFO for transmitting and another for receiving. This is often used when a rare DX station is on the air with many callers. Operating simplex – transmitting and receiving on the same frequency – can result in a lot of confusion with stations trying to hear the DX station while others transmit. By transmitting on one frequency and having callers transmit somewhere else (usually on adjacent frequencies) everyone can hear the DX station and keep “in sync” for more orderly, effective operating.

Answer 174

A: Too strong an input signal can overload a receiver, creating distortion products that interfere with reception of the desired signal. Using an attenuator reduces the input signal level and the possibility of overload.

Answer 175

B: For PSK31 operation, it is important that the output waveform be undistorted. By setting the transmitter output power so that the internal ALC circuit does not activate, that insures the output amplifier is operating with maximum linearity.

Answer 176

D: An oscilloscope visually displays a signal waveform, using one signal to deflect a beam of electrons horizontally across the face of the screen and a second signal to deflect them vertically. The electron beam causes a phosphor coating on the inside of the screen to glow so that the beam’s position can be observed. The horizontal and vertical channel amplifiers in the oscilloscope increase the voltage of the two input signals for the desired amount of deflection. Most oscilloscopes have a built-in oscillator circuit, called a sweep generator, designed to repeatedly deflect the electron beam horizontally across the screen at a fixed rate. With an external signal applied to the vertical amplifier, the sweep generator frequency is adjusted to produce a stable pattern on the screen. Some oscilloscopes also allow a second input signal to be applied to a separate horizontal channel amplifier. This allows two signals to be compared to each other with respect to time.

Answer 177

D: Digital voltmeters display measured values of voltage with excellent precision but they can not measure a complex signal waveform’s time-related parameters, such as its frequency, period, or how it reacts to other signals.

Answer 178

A: An oscilloscope visually displays a signal waveform. This allows you to observe the shape of the CW signal (referred to as the CW envelope) noting, for example, the rise and fall time of the signal. It also allows you to observe problems such as flat-topping (caused by overmodulation) on your SSB signal.

Answer 179

D: When the RF output from a transmitter is connected to the vertical channel of an oscilloscope, the oscilloscope visually displays the signal’s envelope. This allows you to check for signal distortion such as flat-topping (caused by overmodulation). Use an attenuator or RF sampling device to limit the voltage at the oscilloscope input.

Answer 180

D: The higher the impedance of a voltmeter, the smaller the amount of current drawn from the circuit being tested. This allows the voltmeter to make an accurate measurement of voltage while disturbing the circuit as little as possible.

Answer 181

C: A digital voltmeter displays measurements of voltage, current and resistance in numeric form instead of using a moving needle and a fixed scale. That results in significantly better precision than an analog meter. Analog meters, however, may be a better choice for adjusting a circuit for peak and minimum values because the needle movement is easier to see than it is to read changes on a numeric display.

Answer 182

A: A field-strength meter makes a relative measurement of the intensity of the field being radiated from an antenna. If you are doing some radio direction finding (RDF), you may find that a field-strength meter is a handy piece of equipment to use as you get close to the transmitter source. A strong signal may drive the S-meter off scale, requiring a variable attenuator to be used between the directional antenna and receiver as you get closer to the transmitter. A field-strength meter could replace the normal RDF equipment under those conditions, and you can use your body to shield the field-strength meter to indicate the direction to the transmitter.

Answer 183

A: A field-strength meter makes a relative measurement of the intensity of the field being radiated from an antenna. Some amateurs keep a field-strength meter in their shack to monitor the relative RF output from their station. This can be especially handy when you are making antenna or transmitter adjustments

Answer 184

B: A field-strength meter makes a relative measurement of the intensity of the field being radiated from an antenna. By placing the field-strength meter in different locations around the antenna, you can determine the relative field pattern of the antenna.

Answer 185

A: {image src='G4B10.png'}

Answer 186

C: An antenna analyzer is the equivalent of a very low-power, adjustable-frequency transmitter and SWR bridge. The antenna and feed line are connected to the analyzer and SWR measurements are made directly from the analyzer’s meter or display while the analyzer frequency is adjusted. This is much more convenient than using a transmitter and wattmeter and also minimizes the potential for interfering with other signals.

Answer 187

B: An antenna analyzer is the equivalent of a very low-power, adjustable-frequency transmitter and SWR bridge. Because the SWR bridge must be sensitive enough to work with the low-power transmitter, it is also sensitive to RF that the antenna may pick up. This is a particular problem when using the analyzer near broadcast stations with their high-powered transmitters. Symptoms might include SWR readings that change with station programming and excessively high or low SWR that does not change with frequency as expected.

Answer 188

C: An antenna analyzer's manual will show how to make many useful measurements such as feed line characteristic impedance, velocity of propagation, electrical length, and so on. These are very flexible test instruments.

Answer 189

D: The analog meter's moving needle across calibrated scales on the meter face is much easier to adjust for a maximum or minimum value than a numeric display.

Answer 190

A: It is common to test the amplitude linearity of a single-sideband transmitter by injecting two audio tones of equal level into the microphone jack, then observing the pattern made on an oscilloscope. In order to get meaningful results, the two tones must not be harmonically related to each other (such as 1 and 2 kHz). Of course, in order for the audio frequencies to display on the oscilloscope, they must be within the audio passband of the transmitter. The ARRL Lab uses 700 Hz and 1900 Hz tones to perform this test.

Answer 191

B: It is common to test the amplitude linearity of a single-sideband transmitter by injecting two audio tones of equal level into the microphone jack, then observing the pattern made on an oscilloscope. In order to get meaningful results, the two tones must not be harmonically related to each other (such as 1 and 2 kHz). Of course, in order for the audio frequencies to display on the oscilloscope, they must be within the audio passband of the transmitter. The ARRL Lab uses 700 Hz and 1900 Hz tones to perform this test.

Answer 192

B: If radio frequency interference is entering a home audio system through external control cables or power leads, a bypass capacitor can be effective at keeping the unwanted RF signal out of the equipment. With transistor or integrated circuit audio amplifiers you may need to use RF chokes in series with the speaker leads instead of a bypass capacitor. See the ARRL Handbook and The ARRL RFI Book for more information on finding and fixing RFI problems.

Answer 193

C: An arc, such as in motors or at the contacts of electrical equipment, is rich in harmonic energy, even though the primary current may be dc or 60 Hz ac. The resulting RF harmonics can be radiated by the power wiring as broadband noise heard by nearby receivers. Broadband noise can also be caused by intermittent or poor contacts in RF grounds, such as those in your own station.

Answer 194

C: An audio device or telephone can sometimes rectify and detect RF signals in much the same way that a radio does. The audio signal is then amplified resulting in interference. The amateur’s voice will be heard but it will be highly distorted.

Answer 195

A: An audio device or telephone can sometimes rectify and detect RF signals in much the same way that a radio does. The audio signal is then amplified resulting in interference. An amateur’s CW transmission will be heard as on-and-off humming or clicking.

Answer 196

D: One purpose of an amateur station’s RF ground system is to make sure that unwanted signals, such as those picked up from your own transmissions, are directed to ground instead of flowing on or between pieces of equipment. If the ground wire is long enough to be resonant on one or more bands, however, it will present a high impedance, which can enable high RF voltages to be present on the chassis of your equipment or microphone. This can cause an RF burn if the “hot spot” is touched when you are transmitting. {br/}{br/}{image src='Fig G4-01.png'}

Answer 197

C: One purpose of an amateur station’s RF ground system is to make sure that unwanted signals, such as those picked up from your own transmissions, are directed to ground instead of flowing on or between pieces of equipment. If the ground wire is long enough to be resonant on one or more bands, however, it will present a high impedance, which can enable high RF voltages to be present on the chassis of your equipment or microphone. This can cause an RF burn if the “hot spot” is touched when you are transmitting. {br/}{br/}{image src='Fig G4-01.png'}

Answer 198

A: By keeping all of your equipment at the same potential, RF "hot spots" (high voltages) won't be present and RF current that can cause distortion or improper operation won't flow between the enclosures. This is a particularly good strategy when the connection to your ground rod is long enough to be resonant on one or more bands. {br/}{br/}{image src='Fig G4-01.png'}

Answer 199

A: The best solution to many types of interference caused by proximity to an amateur station is to keep the RF signals from entering the equipment in the first place. If filters can be used, they are generally the most effective and least troublesome to install. The next approach is to prevent RF current flow by placing inductance or resistance in its path. This is done by forming the conductor carrying the RF current into an RF choke by winding it around or through a ferrite core. Ferrite beads and cores can also be placed on cables to prevent RF common-mode current from flowing on the outside of cable braids or shields (“common-mode” interference).

Answer 200

D: Ground loops are created when a continuous current path (the loop) exists around a series of equipment enclosures. This loop acts as a single-turn inductor that picks up voltages from magnetic fields generated by power transformers, ac wiring, and other low-frequency currents. The result is a “hum” or “buzz” in audio signals or an ac signal that interferes with control or data signals. Less frequently, the loop can pick up transmitted RF and cause distortion in audio signals. Ground loops can be avoided by using a star-ground or ground bus system where all grounds share a common, low-impedance connection. If interconnections make it impossible to avoid loops, minimize the loop’s area and inductance by bundling cables together.

Answer 201

A: A ground loop can pick up magnetic fields from transformers or ac wiring that result in a “hum” or “buzz” in audio signals or an ac signal that interferes with control or data signals. Less frequently, the loop can pick up transmitted RF and cause distortion in audio signals.

Answer 202

B: Digital Signal Processing (DSP) is the process of converting analog signals to digital data, processing them with software programs, then converting the signals back to analog form. Digital noise reduction is but one application--filtering, demodulation, and decoding are also commonly performed by DSP circuits. {br/}{br/}{image src='Fig G4-02.png'}

Answer 203

A: Because DSP circuits use software to process the digitized signal, the number of different functions that can be performed is only limited by the amount of memory and processing speed. In addition, unlike most analog filters, parameters such as bandwidth and the shape of the response can be made adjustable by the operator. This provides a great deal of flexibility in receiver operation.

Answer 204

B: The software program that controls a DSP notch filter may also operate automatically. In this type of operation, the software searches for the steady tones of an interfering carrier, such as from a shortwave broadcast signal, and then adjusts the frequency of the notch until the amplitude of the carrier’s tone is minimized.

Answer 205

A: A speech processor can improve signal intelligibility by raising average power without increasing peak envelope power (PEP). It does this by bringing up low signal levels while not increasing high signal levels. As a result, the average signal level is higher. A speech processor does not increase the transmitter output PEP.

Answer 206

B: A speech processor can improve signal intelligibility by raising average power without increasing peak envelope power (PEP). It does this by bringing up low signal levels while not increasing high signal levels. As a result, the average signal level is higher. {br/}{br/}{image src='Fig G4-03.png'}

Answer 207

D: Proper adjustment of a speech processor is important to insure your transmitted signal is not distorted and is free of spurious signals. Increasing the amount of processing too far causes your speech to be distorted. Processors that amplify softer speech components more than loud ones will also pick up background noise from fans and other radios and combine them with your desired speech. Another common result of too much processing is overdriving the transmitter output stages, causing interference (“splatter”) to signals on nearby frequencies. Read the owner’s manual for your radio and learn to operate its speech processor correctly.

Answer 208

C: An S meter measures received signal strength in S-units.

Answer 209

D: An ideal S meter operates on a logarithmic scale, indicating one S unit of change for a four-times increase or decrease in power. (This is a 6-dB change in power.) In real life, S meters are only calibrated to this standard in the middle of their range (if at all). Above S9, theoretically corresponding to a 50 µV input signal, S meters are calibrated in dB. In the example of this question, a signal 20 dB stronger than S9 is 100 times stronger than S9.

Answer 210

A: An S meter measures received signal strength and so is found in a receiver or the receive circuits of a transceiver.

Answer 211

C: An ideal S meter operates on a logarithmic scale, indicating one S unit of change for a four-times increase or decrease in power. This is a 6 dB change in power.

Answer 212

C: Nearly all radios display the carrier frequency of a SSB transmission. That means your actual signal lies entirely above (USB) or below (LSB) the displayed frequency. If the sidebands occupy 3 kHz of spectrum, you’ll need to stay far enough from the edge of your frequency privileges to avoid transmitting a signal outside them. For example, Generals are permitted to use up to 14.350 MHz, so the displayed carrier frequency of a USB signal should be no less than 3 kHz from the band edge – 14.347 MHz – and the signal occupy 14.347 to 14.350 MHz. If you transmit higher than that, the sidebands begin to extend into the non-amateur frequencies above 14.350 MHz!. Similarly, using LSB on 40 meters, Generals should operate with the carrier frequency no less than 3 kHz from the band edge -- 7.178 MHz – thus occupying the range of 7.175 to 7.178 MHz. {br/}{br/}{image src='Fig G4-04.png'}

Answer 213

B: Nearly all radios display the carrier frequency of a SSB transmission. That means your actual signal lies entirely above (USB) or below (LSB) the displayed frequency. If the sidebands occupy 3 kHz of spectrum, you’ll need to stay far enough from the edge of your frequency privileges to avoid transmitting a signal outside them. For example, Generals are permitted to use up to 14.350 MHz, so the displayed carrier frequency of a USB signal should be no less than 3 kHz from the band edge – 14.347 MHz – and the signal occupy 14.347 to 14.350 MHz. If you transmit higher than that, the sidebands begin to extend into the non-amateur frequencies above 14.350 MHz!. Similarly, using LSB on 40 meters, Generals should operate with the carrier frequency no less than 3 kHz from the band edge -- 7.178 MHz – thus occupying the range of 7.175 to 7.178 MHz. {br/}{br/}{image src='Fig G4-04.png'}

Answer 214

A: Nearly all radios display the carrier frequency of a SSB transmission. That means your actual signal lies entirely above (USB) or below (LSB) the displayed frequency. If the sidebands occupy 3 kHz of spectrum, you’ll need to stay far enough from the edge of your frequency privileges to avoid transmitting a signal outside them. For example, Generals are permitted to use up to 14.350 MHz, so the displayed carrier frequency of a USB signal should be no less than 3 kHz from the band edge – 14.347 MHz – and the signal occupy 14.347 to 14.350 MHz. If you transmit higher than that, the sidebands begin to extend into the non-amateur frequencies above 14.350 MHz!. Similarly, using LSB on 40 meters, Generals should operate with the carrier frequency no less than 3 kHz from the band edge -- 7.178 MHz – thus occupying the range of 7.175 to 7.178 MHz. {br/}{br/}{image src='Fig G4-04.png'}

Answer 215

B: Nearly all radios display the carrier frequency of a SSB transmission. That means your actual signal lies entirely above (USB) or below (LSB) the displayed frequency. If the sidebands occupy 3 kHz of spectrum, you’ll need to stay far enough from the edge of your frequency privileges to avoid transmitting a signal outside them. For example, Generals are permitted to use up to 14.350 MHz, so the displayed carrier frequency of a USB signal should be no less than 3 kHz from the band edge – 14.347 MHz – and the signal occupy 14.347 to 14.350 MHz. If you transmit higher than that, the sidebands begin to extend into the non-amateur frequencies above 14.350 MHz!. Similarly, using LSB on 40 meters, Generals should operate with the carrier frequency no less than 3 kHz from the band edge -- 7.178 MHz – thus occupying the range of 7.175 to 7.178 MHz. {br/}{br/}{image src='Fig G4-04.png'}

Answer 216

C: To increase the capacitance of a mobile antenna and electrically lengthen it, a structure of rods and possibly a ring is added at or near the top of the antenna. This is called a "capacitance hat" or "capacity hat".

Answer 217

D: The sharp tip of mobile whip can cause corona discharge even at moderate power levels. By adding a smooth ball, the tendency for corona to form is reduced.

Answer 218

A: When you are making the power connections for your 100-watt HF radio for mobile operation, you should connect heavy-gauge wires directly to the battery terminals. Remember that both leads should have fuses, placed as close to the battery as possible. {br/}{br/}{image src='Fig G4-05.png'}

Answer 219

B: The auxiliary socket wiring is adequate for a low-power hand-held radio but probably not for a full-power HF rig drawing 20 amps or more when transmitting. Use a direct connection to the battery using heavy-gauge wire, with both leads fused at the battery.

Answer 220

C: HF mobile antenna systems are the most limiting factor for effective operation of your station. Placing even an 8-foot vertical antenna on top of a small car makes a dangerously tall system. If you have a taller vehicle, this kind of antenna is almost out of the question. Some type of inductive loading to shorten the length is then required. For operation on the 75 meter band this compromise results in a relatively inefficient antenna system.

Answer 221

C: Electrically short antennas have a very low impedance at the feed point. This causes the frequency range to be very narrow over which a matching network presents a 50-ohm impedance to the transmitter.

Answer 222

D: Digital signals internal and external to the vehicle's control computer system can radiate from the vehicle's electrical wiring and be picked up by a mobile radio.

Answer 223

A: Natural sources of energy are becoming more economical and more practical as a way to power your station. Photovoltaic conversion by solar cells and panels converts sunlight into dc electricity.

Answer 224

B: Each photovoltaic cell produces about 0.5 volt in full sunlight if there is no load connected to the cell. The size or surface area of the cell determines the maximum current that the cell can supply.

Answer 225

B: If connected directly to a battery, during periods of low or no illumination, the battery voltage will be higher than that from the panel, allowing the battery to discharge back through the panel.

Answer 226

C: Wind-powered systems provide free energy after the initial cost of installation, but just like solar-powered systems, wind systems need to have a storage battery to supply electricity when the wind is not blowing.

Answer 227

C: Impedance is the opposition to the flow of current in an alternating current (ac) circuit made up of capacitive reactance, inductive reactance, and resistance .

Answer 228

B: The opposition to flow of ac current caused by inductance and capacitance is referred to as reactance. Reactance is one component of impedance, along with resistance.

Answer 229

D: The opposition to flow of ac current caused by inductance and capacitance is referred to as reactance. The opposition to flow of current in an alternating current (ac) circuit caused by an inductor is referred to as inductive reactance.

Answer 230

C: The opposition to flow of ac current caused by inductance and capacitance is referred to as reactance. The opposition to flow of current in an alternating current (ac) circuit caused by a capacitor is referred to as capacitive reactance.

Answer 231

D: The opposition to flow of current caused by the coil in an alternating current (ac) circuit is referred to as inductive reactance. Inductive reactance increases as the ac frequency increases.

Answer 232

A: The opposition to flow of current caused by a capacitor in an alternating current (ac) circuit is referred to as capacitive reactance. This reactance decreases as the ac frequency increases.

Answer 233

D: A power source delivers maximum power to a load when the impedance of the load is equal to (matched to) the impedance of the source. When the impedances are not matched, the power source can not transfer as much power to the load. This is true for both dc power sources (such as batteries or power supplies) and ac power sources (such as transmitters).

Answer 234

A: A power source delivers maximum power to a load when the impedance of the load is equal to (matched to) the impedance of the source. When the impedances are not matched, the power source can not transfer as much power to the load. This is true for both dc power sources (such as batteries or power supplies) and ac power sources (such as transmitters).

Answer 235

B: The ohm is the unit used to measure any opposition to the flow of current. In an ac circuit, this opposition is referred to as impedance which includes both reactance and resistance.

Answer 236

B: The ohm is the unit used to measure any opposition to the flow of current. In an ac circuit, this opposition is referred to as impedance which includes both reactance and resistance.

Answer 237

A: An LC network such as a pi-network uses the exchange of stored energy between the inductor and capacitors to transform the ratio of voltage and current (impedance) between the input and output. Common examples of impedance matching LC networks are the L-, T-, and pi-network, named for the resemblance to a letter of the arrangement of their components on a schematic.

Answer 238

B: An impedance matching transformer changes the ratio of voltage and current between the load and source. Since impedance is the ratio of voltage and current, the transformer can also match different impedances. Matching impedances also maximizes power transfer between the source and load.

Answer 239

D: All of these can alter the ratio of voltage and current in a circuit, effectively changing the impedance as well. A pi-network is an LC-circuit that uses the exchange of stored energy between the inductor and capacitors to transform the ratio of voltage and current (impedance) between the input and output. Special lengths of transmission lines (called “stubs”) set up patterns of reflections in the feed line that cancel the reflections from a mismatched load, making the load impedance appear as if it was the same as that of the feed line.

Answer 240

B: {image src='G5B01.png'} {br/}{br/}{image src='TabG5B01.png'}

Answer 241

C: In a circuit with several parallel branches, the total current flowing into the junction of the branches is equal to the sum of the current through each branch. This is Kirchoff’s Current Law. {br/}{br/}{image src='Fig G5-01.png'}

Answer 242

B: {image src='G5B03.png'} {br/}{br/}{image src='Fig G5-02.png'}

Answer 243

A: Use the Power Circle drawing to find the equation to calculate power. The power in a circuit is equal to the voltage times the current: P = I x E = 0.2 x 12 = 2.4 watts

Answer 244

A: Use the Ohm’s Law Circle and Power Circle drawings to find the equations to calculate power. Since P = I × E and E = R × I, the power in a circuit can also be expressed as P = I × I × R, so P = 0.007 × 0.007 × 1250 = 0.06125 W = 61.25 mW. Remember that 7 milliamperes is equal to 0.007 ampere, 1.25 kilohms is equal to 1250 ohms and 0.06125 watt is equal to approximately 61 milliwatts.

Answer 245

B: PEP is the output power measured at the peak of the RF cycle at the peak of the signal’s envelope and is equal to: {br/}{br/}{image src='G5B06.png'}

Answer 246

C: RMS, or root mean square, voltage values convert a constantly-varying ac voltage to the equivalent of a constant dc voltage. The RMS value of an ac voltage is the value that would deliver the same amount of power to a resistance as a dc voltage of the same value.

Answer 247

D: If you know the RMS voltage and want to know the peak value, multiply the RMS by the square root of 2 (which is 1.414). If you want to know peak-to-peak, double the result. In this case, 120 × 1.414 × 2 = 339.4 V. {br/}{br/}{image src='Fig G5-03.png'}

Answer 248

B: If you know the peak voltage, you can find the RMS value by multiplying the peak voltage by 0.707 (which is the same as dividing by the square root of 2). 17 × 0.707 = 12 V. {br/}{br/}{image src='Fig G5-04.png'}

Answer 249

C: {image src='G5B10-1.png'} {br/}{br/}{image src='G5B10-2.png'}

Answer 250

B: It’s 1.0 because for an unmodulated carrier all RF cycles have the same voltage, meaning that the envelope’s average and peak values are the same.

Answer 251

B: It’s 245 V because P = E2 / R, so E = √(1200 / 50). This is the RMS voltage across the 50-W load.

Answer 252

B: The PEP and average power of an unmodulated carrier are the same. For an unmodulated carrier all RF cycles have the same voltage, meaning that the envelope’s average and peak values are the same.

Answer 253

B: {image src='G5B14.png'}

Answer 254

C: {image src='G5C01.png'} {br/}{br/}{image src='Fig G5-05.png'}

Answer 255

B: The primary winding is generally considered to be the input. However energy can flow in either direction, primary-to-secondary or secondary-to-primary.

Answer 256

B: Add additional resistors in series to increase the total resistance.

Answer 257

C: {image src='G5C04.png'}

Answer 258

C: {image src='G5C05.png'}

Answer 259

C: {image src='G5C06.png'}

Answer 260

A: {image src='G5C07.png'}

Answer 261

D: {image src='G5C08.png'}

Answer 262

C: {image src='G5C09.png'}

Answer 263

C: {image src='G5C10.png'}

Answer 264

C: {image src='G5C11.png'}

Answer 265

B: {image src='G5C12.png'}

Answer 266

C: Add additional capacitors in parallel to increase the total capacitance.

Answer 267

D: Add additional inductors in series to increase the total inductance.

Answer 268

A: {image src='G5C15.png'}

Answer 269

A: It is important to use filter capacitors that have a low equivalent series resistance (ESR) rating for the output filter of a switching power supply. Low ESR means that currents flowing into and out of the capacitor as it smoothes the output voltage will not cause ripple (voltage variations) and losses that heat the capacitor.

Answer 270

D: Because electrolytic capacitors can be made with the required high capacitance value in a small package, they are often used in power supply circuits to filter the rectified ac voltage.

Answer 271

D: The primary advantage of ceramic capacitors is that they offer good performance at low cost. Ceramic capacitors are usually used as bypass capacitors that filter out high-frequency ac voltages from dc and low-frequency signal connections. {br/}{br/}{image src='Fig G6-01.png'}

Answer 272

C: Electrolytic capacitors are designed to provide large values of capacitance for energy storage and ac voltage filtering. Their construction, shown in the illustration, provides relatively high capacitance in a small volume. The tradeoff is that dc voltage applied to them must always be of the same polarity and the manufacturing technique leads to rather wide variations in capacitance. {br/}{br/}{image src='Fig G6-01.png'}

Answer 273

A: Lead inductance creates a small inductance in series with the capacitor. At low frequencies, lead inductance can be ignored but at VHF and higher frequencies, the inductive reactance begins to cancel the capacitor’s own reactance, reducing the effective capacitance dramatically! Capacitors to be used at these high frequencies must have very short leads.

Answer 274

C: The resistance of almost any substance changes when heated. The amount of change in a resistor’s value depends on its temperature coefficient. Most resistors have a positive temperature coefficient, meaning that resistance increases with temperature.

Answer 275

B: Wire-wound resistors are made exactly as their name implies. A length of “resistance wire” — usually Nichrome — is wound around a ceramic form. The wire has some specific resistance per length of wire, so the length of wire is chosen to give the desired resistance. Because a long length of wire is difficult to accommodate in an electronics circuit, the wire is wound on the form to reduce the overall length of the resistor. The resistor is then coated with a ceramic or other insulating material to protect the wire. If this construction method sounds like an inductor to you, you are absolutely correct! It is not a good idea to use wire-wound resistors in any RF circuits or anywhere you don’t want some extra amount of inductance to be included in the circuit. The extra inductance will detune any resonant circuit of which it is part or add unwanted inductive reactance to signal paths.

Answer 276

B: All resistors change value to some degree with temperature. A thermistor is a special type of resistor whose change in value with temperature is precisely controlled so that it can be used as a temperature sensor.

Answer 277

D: {image src='G6A09.png'}

Answer 278

C: An inductor that is formed by winding a coil of wire on a straight coil form of either air or a magnetic material is called a solenoid inductor. The magnetic field associated with a solenoid core extends through the center of the core and then around the outside of the coil. To minimize any interaction between the magnetic fields around solenoid inductors in a circuit, the coils should be placed so that the axes along which the wire is wound are at right angles to each other. (To ensure minimum interaction between solenoid coils you might also have to place each inductor inside its own shielded enclosure.) {br/}{br/}{image src='Fig G6-03.png'}

Answer 279

B: It is important to minimize unwanted mutual inductance between two inductors to prevent coupling – transferring energy – between different circuit stages. {br/}{br/}{image src='Fig G6-03.png'}

Answer 280

D: A filter choke is an inductor that is connected in series with the output of a power supply. It works with the filter capacitor to smooth the rectified ac from the rectifier into dc. The inductor is called a choke because it “chokes off” the variations in voltage at its input.

Answer 281

B: Inter-turn capacitance is created by adjacent turns of wire separated by air or their insulation. Even though the turns of wire are connected, the small separation between the wire surfaces creates a small capacitance. In a coil of many turns, the inter-turn capacitance can become significant. At high frequencies, the combination of the coil’s inductance and the inter-turn capacitance can become a series- or parallel-resonant circuit!

Answer 282

C: Power-supply rectifier diodes are made from semiconductor material. Diodes allow current to flow only in one direction. If the voltage is high enough, however, current can be forced to flow in the opposite direction, often destroying the diode. The peak inverse voltage rating (PIV) of a rectifier diode is the maximum reverse voltage that should ever be applied to the diode--it is guaranteed to withstand that voltage.

Answer 283

A: Peak inverse voltage and average forward current are two major ratings that must not be exceeded for silicon diode rectifiers. The peak inverse voltage rating (PIV) of a rectifier diode is the maximum reverse voltage that should ever be applied to the diode--it is guaranteed to withstand that voltage. The maximum average forward current is the other major rating that must not be exceeded. Forward current causes power to be dissipated in the diode due to the forward voltage drop (0.7 volts in silicon rectifiers). The amount of power is 0.7 V times the average forward current. Too much current overheats and destroys the diode.

Answer 284

B: The junction threshold voltage is the voltage at which a diode begins to conduct significant current across its PN junction. The amount of voltage depends on the material from which the diode is constructed. The junction threshold voltage of silicon diodes is approximately 0.7 V and for germanium diodes approximately 0.3 V.

Answer 285

C: Two or more diodes are sometimes connected in parallel to increase the current-handling ability of a circuit. There should always be a small resistor connected in series with each parallel diode. Without a resistor in series with each diode, one diode may conduct most of the current because of small variations in threshold voltage and that could destroy the diode by exceeding its average forward current rating. The resistor value should be chosen to provide a few tenths of a volt drop at the expected forward current. {br/}{br/}{image src='Fig G6-02.png'}

Answer 286

C: The junction threshold voltage is the voltage at which a diode begins to conduct significant current across its PN junction. The amount of voltage depends on the material from which the diode is constructed. The junction threshold voltage of silicon diodes is approximately 0.7 V and for germanium diodes approximately 0.3 V.

Answer 287

A: The construction of a Schottky diode results in much lower capacitance between the cathode and the anode. This makes the diode respond better to high-frequency signals in a switching power supply, digital logic, or an RF circuit.

Answer 288

A: When a bipolar transistor is used as a switch in a logic circuit it is important that the switch either be “all the way on” or “all the way off.” This is achieved by operating the transistor either in its saturation region to turn the switch on, or in its cut-off region to turn the switch off.

Answer 289

D: On some power transistors the collector is connected to the case to improve the transfer of heat away from the semiconductor material. This helps keep the transistor from overheating when controlling high currents but requires that the case of the transistor (usually connected to the collector) be insulated from ground since most circuits do not ground the collector.

Answer 290

B: A MOSFET (Metal Oxide Semiconductor Field Effect Transistor) is similar to a JFET (Junction Field Effect Transistor), but instead of the gate electrode being in direct contact with the channel between drain and source, it is insulated by a thin insulating layer of oxide. The gate voltage still controls electron flow between the drain and source, but very little current flows in the gate circuit.

Answer 291

A: The control grid is closest to the cathode, the element of the tube that generates the electrons. By varying the control grid voltage with respect to the cathode voltage, electron flow between cathode and plate can be controlled.

Answer 292

B: A Field-Effect Transistor (FET) acts very much like a vacuum tube with the gate electrode taking the role of the control grid, controlling electron flow between the drain and source that correspond to the plate and cathode, respectively.

Answer 293

A: The screen grid is placed between the plate and control grid and kept at a constant voltage. This isolates the control grid from the plate and reduces the capacitance between them.

Answer 294

B: Nickel-Cadmium (NiCd) batteries are constructed so that they can supply large quantities of current very quickly. This makes them useful in portable power tools and radio transceivers.

Answer 295

C: Standard 12-volt lead-acid batteries are composed of six 2-volt cells connected in series. Each cell should not be discharged below 1.75 volts to avoid causing irreversible chemical changes that damage the cell. Thus, the minimum voltage for a standard 12-volt battery is 6 x 1.75 = 10.5 volts.

Answer 296

D: Carbon-zinc batteries are not rechargeable because the chemical reaction that powers them cannot be reversed. Do not attempt to recharge them! If current is forced back through the cell, the resulting chemical reaction releases acid and heat that may breach the battery’s case, damaging whatever houses the battery.

Answer 297

D: A linear voltage regulator is composed of a transistor, a voltage reference diode, and an amplifier that compares the circuit output voltage to the voltage reference. The regulator continuously varies the transistor current to keep the output voltage constant. Operation over a continuous range of voltages and currents is what analog integrated circuits do.

Answer 298

B: An MMIC is a special type of analog IC containing circuits to perform RF operations such as amplification, modulation and demodulation, and mixing at HF through microwave frequencies. Some MMICs combine several functions, acting as an entire receiver front end, for example. The MMIC is what enables communications engineers to construct low-cost, hand-held mobile phones and GPS receivers, among other sophisticated examples of wireless technology.

Answer 299

A: Integrated circuits based on CMOS (Complementary Metal Oxide Semiconductor) technology consume very little current when operating, only drawing significant power when switching between ON and OFF states.

Answer 300

B: ROM, or read only memory, contains data or program instructions that do not need to be changed. ROM is used to prevent unauthorized changes.

Answer 301

C: Non-volatile memory can retain stored data even if power is removed and restored. It never needs to have the data “refreshed.” Volatile memory loses the data if power is removed and often needs to have the data refreshed while in operation, such as for dynamic types of memory.

Answer 302

D: An operational amplifier, or op amp, is an analog circuit, operating over a continuous range of voltage and current.

Answer 303

D: Incandescent indicators (lamps) are bright but they waste as heat most of the energy supplied to them. For the same amount of light output, LEDs are much more power-efficient than incandescents.

Answer 304

D: An LED emits light when forward biased so that current flows through the PN-junction of the diode. Photons of light are given off when the electrons from the N-type material combine with the holes in the P-type material.

Answer 305

A: A liquid crystal display (LCD) works by blocking the transmission of light through an otherwise transparent layer of liquid crystals. Transparent electrodes are printed on the glass layers on either side of the liquid crystals to form the pattern of the digits, characters, and symbols. When voltage of the right polarity is applied between the electrodes, the liquid crystals twist into a pattern that blocks light. This is why an LCD requires ambient light to reflect off the back of the display or an active source of light behind the liquid crystals (back-lighting) in order to see the desired pattern.

Answer 306

A: A USB (Universal Serial Bus) interface is a means of exchanging digital data in a serial stream (meaning one bit at a time). The computer and transceiver are the most likely to communicate over such an interface.

Answer 307

B: These miniature computers on a single IC consist of thousands of digital gates and logic elements that can retrieve program instructions (known as machine language) and execute them using digital data. Simple microprocessors may be little more than a set of registers that store and exchange data for the program instructions. Complex microprocessors may contain sub-processors that are dedicated to special functions, sophisticated communications interfaces, or include analog-digital converters to provide an all-in-one DSP platform.

Answer 308

D: RS-232 serial data interfaces are common in amateur equipment. The most common connector used for these interfaces is the 9-pin D-style DE-9, also called a DB-9. These connectors are usually found on personal computers as COM ports. RS-232 interfaces are being phased out in favor of USB and other interfaces that can transfer data at higher rates.

Answer 309

C: The UHF connector family includes the PL-259 cable plug and SO-239 chassis-mounted socket. It is the most popular type of RF connector used on amateur equipment. UHF does not refer to a frequency range in this case.

Answer 310

C: The RCA phono connector is the most common audio signal connector for consumer electronics and a great deal of amateur equipment. The connector’s name derives from its early use by the RCA Company for audio connectors and its subsequent popularity for the connection of phonographs to amplifiers and receivers.

Answer 311

B: A keyed connector has an asymmetrical body shape or arrangement of contacts. This prevents reversed or improper circuit connections that lead to improper operation or damage to the equipment. Do not force keyed connectors together if they are not oriented correctly.

Answer 312

A: Type N connectors are connectors for coaxial cable used at HF, VHF, UHF, and microwave frequencies up to 10 GHz. The type N connector shell is threaded like a PL-259, but the special design of its body presents the same 50-W impedance as coaxial cable so no signals are reflected or lost at the junction of connector and feed line. Type N connectors also have special gaskets built-in so that they are waterproof without requiring additional coatings.

Answer 313

C: Multiple-pin DIN and Mini-DIN connectors are the standard for accessory connectors on amateur equipment. DIN stands for the Deutsches Institut für Normung, the German standards organization. DIN and Mini-DIN connectors are keyed and have up to 9 pins.

Answer 314

B: SMA connectors are small threaded connectors designed for miniature coaxial cable and are rated for use up to 18 GHz. Handheld transceivers often use SMA connectors for attaching antennas.

Answer 315

B: A bleeder resistor connected across a filter capacitor discharges the capacitor when power is not supplied to the circuit. This minimizes the risk of electrical shock if the supply enclosure is opened, exposing the capacitor terminals. {br/}{br/}{image src='ARRL0089.png'}

Answer 316

D: A power supply filter network consists of capacitors and inductors used to smooth out the pulses of voltage and current from the rectifier. Capacitors oppose changes in voltage while the inductors oppose changes in current. The combination results in a constant dc output voltage from the supply. {br/}{br/}{image src='Fig G7-02.png'}

Answer 317

D: In the full-wave center-tapped rectifier, when a rectifier diode is not conducting it must withstand not only the negative peak voltage from its own half of the winding but the positive voltage from the other winding. Thus the peak inverse voltage applied to the diodes is twice the normal peak output voltage of the supply. In a bridge rectifier circuit the applied PIV to either diode is only the peak ouput voltage. {br/}{br/}{image src='Fig G7-03.png'}

Answer 318

D: The peak inverse voltage applied to the rectifier diode in a half-wave rectifier circuit is twice the supply's peak output voltage because the filter capacitor charges to the peak transformer voltage during the half-cycle when the diode is conducting. During the half-cycle when the diode is not conducting, the capacitor remains charged while the transformer output voltage reaches a peak value of the opposite polarity. Thus the peak inverse voltage is twice the normal peak output voltage of the supply. {br/}{br/}{image src='Fig G7-03.png'}

Answer 319

B: Since there are 360 degrees in a full cycle of ac, a half-wave rectifier converts 180 degrees of the ac input waveform to dc. {br/}{br/}{image src='Fig G7-03.png'}

Answer 320

D: Since there are 360 degrees in a full cycle of ac, a full-wave rectifier converts 360 degrees of the ac input waveform to dc. {br/}{br/}{image src='Fig G7-03.png'}

Answer 321

A: A full-wave rectifier changes alternating current with positive and negative half cycles into a fluctuating current with all positive pulses. Since the current in this case has not yet been filtered, it is a series of pulses at twice the frequency of the ac input. {br/}{br/}{image src='Fig G7-03.png'}

Answer 322

C: Switched-mode power supplies operate at a frequency much higher than the 60 Hz ac line current. (Oscillator frequencies of 50 kHz or more are commonly used.) This allows the use of small, lightweight transformers. While the transformer in a linear power supply capable of supplying 20 amperes might weigh 15 or 20 pounds, the transformer for a switched-mode power supply with a similar current rating might weigh 1 or 2 pounds! Switched-mode power supplies have more complex circuits than linear supplies and generally require more components than a simple linear supply.

Answer 323

A: Microcontrollers are a special type of microprocessor designed to interact with external sensors and circuits to control or operate a piece of equipment, such as an automatic antenna tuner or electronic keyer.

Answer 324

A: Binary numbers are easily represented by circuits that have two stable states--ON and OFF. The states can be used to represent either a binary 0 or 1 as the designer chooses.

Answer 325

B: If both inputs to an AND gate are true or “1”, the AND function output is also “1”, otherwise the output is "0". {br/}{br/}{image src='Fig G7-08.png'}

Answer 326

C: A NOR (NOT-OR) gate consists of an OR gate with its output inverted. If either or both of the inputs to a two-input NOR gate are true or “1”, the OR function is also “1”, which is then inverted to “0” at the output. {br/}{br/}{image src='Fig G7-08.png'}

Answer 327

C: There are 8 states because the number of states in a binary counter is 2N, where N is the number of bits in the counter. A 2-bit counter has 22 = 4 states, a 3-bit counter 23 = 8 states, a 4-bit counter 24 = 16 states, and so forth.

Answer 328

A: A shift register consists of a sequence of flip-flop circuits connected output-to-input and sharing a common clock input signal. With each pulse of the clock signal, the state of the input signal (0 or 1) to the shift register is transferred to the output of the first flip-flop and each subsequent flip-flop’s output is passed to the next flip-flop’s input.

Answer 329

D: To make an oscillator requires an amplifier and a circuit that routes some of the amplifier’s output signal back to the input (called a “feedback loop”) such that it is reinforced in the amplifier output. This is called positive feedback. A filter in the feedback loop is used so only signals at the desired frequency are reinforced. Starting with random noise, the oscillator gradually builds up an output signal at the filter frequency until it is self-sustaining.

Answer 330

B: Efficiency is defined as the total output power divided by the total input power and is measured in percent. For an RF amplifier, total output power is measured by a wattmeter. The total input power is the dc power required for the amplifier to operate. For example, if to produce 1200 watts of RF output the amplifier requires 1000 mA of plate current at a voltage of 2000 V, efficiency = 1200 watts / (1 A × 2000 V) = 1200 / 2000 = 60%.

Answer 331

C: To make an oscillator requires an amplifier and a circuit that routes some of the amplifier’s output signal back to the input (called a “feedback loop”) such that is reinforced in the amplifier output. A filter in the feedback loop is used so only signals at the desired frequency are reinforced. An LC oscillator uses a parallel LC circuit (a tank circuit) as the filter in the feedback loop.

Answer 332

D: Class A amplifiers are used when low distortion is required. Class A means that current flows in the amplifying device – whether a transistor or vacuum tube – at all times. Because the amplifier is never saturated or cut off, its operation can be optimized for linear reproduction of the input signal. The tradeoff is that Class A amplifiers consume power 100% of the time, require a source of bias to keep them on in the absence of an input signal, and aren’t particularly efficient.

Answer 333

B: A Class C amplifier conducts current during less than half of the input signal cycle, resulting in high distortion. This rules out Class C amplifiers for any form of amplitude modulation, such as SSB or AM. Class C amplifiers can be used for CW since that mode requires only the presence or absence of a signal. Similarly, Class C is suitable for FM signals that only depend on signal frequency, which is not changed by the amplifier. Class C amplifiers generate significant harmonics, so they require filtering for use as transmitter outputs.

Answer 334

D: Class C amplifiers act a lot like switches--they turn on for a fraction of the input signal’s cycle and stay off the rest of the time. While these amplifiers are not linear at all and require filters to eliminate the harmonics in their output, they are quite efficient.

Answer 335

B: Neutralization of a power amplifier is a technique that minimizes or cancel the effects of positive feedback. Positive feedback occurs when the output signal is fed back to the input in phase with the input signal, creating an oscillator. Neutralization consists of feeding a portion of the amplifier output back to the input, 180 degrees out of phase with the input, to cancel the positive feedback. This is called negative feedback. Self-oscillation creates powerful spurious signals that cause interference. Self-oscillations can also be sufficiently powerful to damage the amplifier. {br/}{br/}{image src='Fig G7-05.png'}

Answer 336

B: A linear amplifier is defined as one whose output waveform is a copy of the input waveform, although larger in amplitude. Hams refer to power amplifiers as “linears”, whether they are operating linearly (for AM or SSB modes) or not (for CW or FM). It is important to understand when linear operation is important. An amplifier designed for FM will not be suitable as an SSB amplifier, for example.

Answer 337

B: In a single-sideband transmitter, the modulating audio is added to the RF signal in the balanced modulator. The balanced modulator also balances out or cancels the original carrier signal, leaving a double-sideband, suppressed-carrier signal. A filter then removes one of the sidebands, leaving a single-sideband signal that is sent to the mixer, where it combines with the signal from a Local Oscillator (LO) to produce the RF signal that is amplified and sent to the antenna. The LO shown in the figure is crystal-controlled for fixed-frequency operation. Replacing the crystal-controlled LO with a variable-frequency oscillator (VFO) results in a tunable transmitter similar to those in most modern transceivers. {br/}{br/}{image src='Fig G7-06.png'}

Answer 338

D: In a single-sideband transmitter, the modulating audio is added to the RF signal in the balanced modulator. The balanced modulator also balances out or cancels the original carrier signal, leaving a double-sideband, suppressed-carrier signal. A filter then removes one of the sidebands, leaving a single-sideband signal that is sent to the mixer, where it combines with the signal from a Local Oscillator (LO) to produce the RF signal that is amplified and sent to the antenna. The LO shown in the figure is crystal-controlled for fixed-frequency operation. Replacing the crystal-controlled LO with a variable-frequency oscillator (VFO) results in a tunable transmitter similar to those in most modern transceivers. {br/}{br/}{image src='Fig G7-06.png'}

Answer 339

C: In a superheterodyne receiver, the mixer combines signals from the RF amplifier and the local oscillator (LO) then sends those signals to the IF filter, which passes the desired range of frequencies while rejecting the signals at higher and lower frequencies. {br/}{br/}{image src='Fig G7-07.png'}

Answer 340

D: In a superheterodyne receiver, the product detector circuit recovers the modulating audio signal by combining the output of the intermediate frequency (IF) amplifier and the beat frequency oscillator (BFO). The recovered audio signal is then passed to the audio frequency (AF) amplifier. {br/}{br/}{image src='Fig G7-07.png'}

Answer 341

D: The direct digital synthesizer or DDS replaces the analog VFO circuits with a digital circuit that creates a sine wave as a series of small steps. The duration and amplitude of each step is precisely controlled based on a crystal oscillator. This allows a DDS to act as an oscillator with stability that is comparable to that of a crystal oscillator, while still being adjustable over a wide range.

Answer 342

B: To prevent unwanted reflected power and elevated SWR, keep all elements of the feed line and antenna system at the same impedance. A low-pass filter, designed to be installed at the transmitter output, should have the same impedance as the transmission line.

Answer 343

C: By definition, a superheterodyne receiver must contain a mixer and a local oscillator. One additional stage, a detector, is necessary to recover the modulating audio. Thus, the simplest superheterodyne consists of a mixer, oscillator, and detector. Practical receivers add more amplifiers to improve sensitivity and filters to reject unwanted signals. {br/}{br/}{image src='Fig G7-07.png'}

Answer 344

D: A frequency discriminator converts the variations in frequency of the limiter’s output signal into amplitude variations, recovering the modulating audio signal. A quadrature detector is another type of FM demodulation circuit that converts changes in frequency into amplitude variations. {br/}{br/}{image src='Fig G7-08B.png'}

Answer 345

D: Digital Signal Processing (DSP) is the process of converting analog signals to digital data, processing them with software programs, then converting the signals back to analog form. Digital noise reduction is but one application--filtering, demodulation, and decoding are also commonly performed by DSP circuits. {br/}{br/}{image src='Fig G4-02.png'}

Answer 346

B: Digital Signal Processing (DSP) is the process of converting analog signals to digital data, processing them with software programs, then converting the signals back to analog form. Digital noise reduction is but one application--filtering, demodulation, and decoding are also commonly performed by DSP circuits. {br/}{br/}{image src='Fig G4-02.png'}

Answer 347

A: In a software-defined radio (SDR) nearly all of the radio's functions are performed by digital hardware. This allows the radio's operation to be changed and controlled by software without having to change the way in which the radio is physically constructed.

Answer 348

D: There are several ways to change or modulate an RF wave for the purpose of conveying information. CW simply turns the signal on and off to convey information. Amplitude modulation changes the strength or amplitude of the wave while frequency modulation changes its frequency. Phase modulation conveys information by changing the phase of the wave. {br/}{br/}{image src='Fig G8-01.png'}

Answer 349

B: There are several ways to change or modulate an RF wave for the purpose of conveying information. CW simply turns the signal on and off to convey information. Amplitude modulation changes the strength or amplitude of the wave while frequency modulation changes its frequency. Phase modulation conveys information by changing the phase of the wave. {br/}{br/}{image src='Fig G8-02.png'}

Answer 350

D: There are several ways to change or modulate an RF wave for the purpose of conveying information. CW simply turns the signal on and off to convey information. Amplitude modulation changes the strength or amplitude of the wave while frequency modulation changes its frequency. Phase modulation conveys information by changing the phase of the wave. {br/}{br/}{image src='Fig G8-03.png'}

Answer 351

B: Reactance modulators are the most common method of generating (phase modulation) PM signals. Phase modulators cause the output signal phase to vary with both the modulating signal’s amplitude and frequency. {br/}{br/}{image src='Fig G8-04.png'}

Answer 352

D: In an AM transmission, at any given instant the amplitude or envelope of the RF signal changes according to the modulating audio signal.

Answer 353

C: In a single-sideband, suppressed-carrier, amplitude-modulated transmitter, the RF carrier signal is reduced or suppressed. The less energy that is used by the carrier the more power that can be put into the sidebands. This increases the efficiency of the system. {br/}{br/}{image src='Fig G8-05.png'}

Answer 354

A: In a single-sideband (SSB) amplitude-modulated transmitter, the RF carrier signal is reduced or suppressed, and one of the sidebands is removed. Suppression of the carrier allows more power to be put into the sideband. Because the carrier is suppressed and one sideband is filtered out, only enough frequency bandwidth is required to transmit a single sideband. This has the narrowest bandwidth of all the popular phone emissions. The bandwidth of an SSB signal is between about 2 and 3 kHz, the bandwidth of a double-sideband AM signal is about 6 kHz and the bandwidth of frequency and phase modulated phone signals is about 16 kHz.

Answer 355

D: When an SSB signal is overmodulated the output waveform of the signal is distorted, which causes spurious emissions outside the normal bandwidth of the signal. When an FM or PM signal is overmodulated, the deviation of the signal becomes too high and again, spurious emissions appear outside the normal bandwidth of the signal. In both cases, the spurious emissions cause interference to other stations. {br/}{br/}{image src='Fig G8-06.png'}

Answer 356

B: To reduce overmodulation, the Automatic Level Control (ALC) circuit reduces microphone gain when it detects excessive audio levels. For proper adjustment on most transmitters, the microphone gain control should be adjusted so that there is a slight movement of the ALC meter on modulation peaks.

Answer 357

C: The figure shows an overmodulated signal (B) as seen on an oscilloscope with flattening at the maximum levels of the envelope. This is referred to as flat-topping. {br/}{br/}{image src='Fig G8-07.png'}

Answer 358

A: Frequency Modulation (FM) results when the modulating signal causes the frequency of an oscillator to change in proportion to the modulating signal’s amplitude. If the oscillator’s frequency changes in proportion to both the modulating signal’s amplitude and frequency, the result is phase modulation (PM).

Answer 359

A: {image src='G8A12.png'}

Answer 360

A: The mixer stage in a receiver combines the input signal with an oscillator signal to produce the sum and the difference of the two signals. Filters or mixer design will give one desired new signal, known as the intermediate frequency (IF) signal. For example, if a 13.795 MHz variable frequency oscillator (VFO) signal is mixed with a 14.25 MHz RF signal, it will produce new signals at 28.045 MHz and 0.455 MHz, or 455 kHz. A filter is used to remove the 28.045 MHz signal and pass the 455 kHz IF signal.

Answer 361

B: {image src='G8B02.png'}

Answer 362

A: The process of mixing signals is known as heterodyning. A receiver that mixes a local oscillator (LO) signal with a received RF signal to produce a signal at some intermediate frequency (IF) that is higher in frequency than the baseband audio signal is called a superheterodyne receiver, or a superhet. The IF signal is processed further by filtering and amplifying it, and then converting the signal to baseband audio. The audio signal is further amplified and fed to a speaker or is connected to headphones so you can hear the received signal.

Answer 363

D: An FM transmitter often makes use of a device called a frequency multiplier. In a VHF FM transmitter, a reactance modulator operates on a radio-frequency oscillator that is normally operating in the high-frequency (HF) range. A frequency multiplier doubles or triples the frequency of the modulated signal, usually by generating harmonics of the modulated HF signal and selecting one for output to the next stage in the transmitter. Sometimes several multiplier stages are required to produce a signal at the desired output frequency.

Answer 364

C: FM phone signals have a bandwidth of about 16 kHz. At frequencies below 29.5 MHz, the maximum FCC allowable bandwidths are narrower than 16 kHz. The HF bands are relatively narrow, and would not be able to accommodate many wide bandwidth FM signals.

Answer 365

D: {image src='G8B06.png'}

Answer 366

B: {image src='G8B07.png'}

Answer 367

B: {image src='G8B08.png'}

Answer 368

D: By matching the receiver bandwidth and the signal bandwidth, noise outside the signal's bandwidth is rejected and no necessary signal energy is discarded. Both result in improvement of the signal-to-noise ratio (SNR).

Answer 369

A: PSK31 is a digital mode that transmits symbols at a rate of 31.25 baud.

Answer 370

C: Forward error correction (FEC) is the practice of sending redundant data in the transmitted packet that allows the receiver to correct some types of errors that may be caused by noise, fading, or interference. There are a number of FEC methods involving special codes.

Answer 371

B: Advanced modulation techniques can pack multiple bits of data into each transmitted symbol, but it is the symbol rate that sets a minimum limit on bandwidth. Increasing the rate at which symbols are transmitted requires more signal bandwidth in order to maintain a minimum signal-to-noise ratio.

Answer 372

A: The characteristic impedance of a parallel-conductor feed line depends on the distance between the conductor centers and the radius of the conductors. {br/}{br/}{image src='Fig G9-01.png'}

Answer 373

B: Common coaxial cables used as antenna feed lines have characteristic impedances of 50 or 75 ohms. {br/}{br/}{image src='Fig G9-02.png'}

Answer 374

D: The flat ribbon type of feed line often used with TV antennas has a characteristic impedance of 300 ohms. This feed line is called twin lead. {br/}{br/}{image src='Fig G9-01.png'}

Answer 375

C: {image src='G9A04.png'}

Answer 376

B: Feed line loss is greater at higher frequencies. For example, if you were to use the same type of coaxial cable for your 160 meter antenna as for your 2 meter antenna, there would be much more loss at the higher 2 meter frequencies.

Answer 377

D: RF feed line loss is normally specified in decibels of loss for each 100 feet of line. Loss must also be specified at a certain frequency.

Answer 378

D: To eliminate reflected power, the antenna impedance must be matched to the characteristic impedance of the feed line. If the impedances are matched, all of the feed line power is transferred to the antenna. The problem with reflected power causing standing waves and raising the feed line SWR is not generally transmitter efficiency but rather the transmitter’s reaction to the high SWR. Modern solid-state transmitters usually have protection circuitry that reduces the power output in the presence of high SWR. (When the SWR is high there are high voltages present that can damage components.) By reducing SWR, the transmitter can operate at maximum power output.

Answer 379

B: A matching network at the transmitter does not change the SWR on the feed line, so the feed line SWR is still 5:1.

Answer 380

A: If a load connected to a feed line is purely resistive, the SWR can be calculated by dividing the line characteristic impedance by the load resistance or vice versa, whichever gives a value greater than one. 200 / 50 = 4:1 SWR.

Answer 381

D: If a load connected to a feed line is purely resistive, the SWR can be calculated by dividing the line characteristic impedance by the load resistance or vice versa, whichever gives a value greater than one. 50 / 10 = 5:1 SWR.

Answer 382

B: If a load connected to a feed line is purely resistive, the SWR can be calculated by dividing the line characteristic impedance by the load resistance or vice versa, whichever gives a value greater than one. 50 / 50 = 1:1 SWR.

Answer 383

A: If a load connected to a feed line is purely resistive, the SWR can be calculated by dividing the line characteristic impedance by the load resistance or vice versa, whichever gives a value greater than one. 50 / 25 = 2:1 SWR.

Answer 384

C: If a load connected to a feed line is purely resistive, the SWR can be calculated by dividing the line characteristic impedance by the load resistance or vice versa, whichever gives a value greater than one. 300 / 50 = 6:1 SWR.

Answer 385

B: A random-wire antenna consist of a wire connected directly to the transmitter at one end. It can be of any length because an antenna tuner is used to match the impedances. It does not require a feed line because the single piece of wire serves as both a feed line and an antenna. It is considered to be a multiband antenna because the antenna tuner will match the impedances for several frequency bands. One significant disadvantage of a random-wire antenna is that you may experience RF “hot spots” in your station because the station equipment and ground system are part of your antenna system!

Answer 386

D: A ground-plane antenna is often constructed with a ¼-wavelength vertical radiating element and four ¼-wavelength horizontal “radial” wires that form the ground plane. You can change the impedance of a ground-plane antenna by changing the angle of the radials. Bending or sloping the radials downward to about a 45-degree angle will increase the impedance from approximately 35 ohms to approximately 50 ohms, reducing SWR. {br/}{br/}{image src='Fig G9-03.png'}

Answer 387

B: A ground-plane antenna is often constructed with a ¼-wavelength vertical radiating element and four ¼-wavelength horizontal “radial” wires that form the ground plane. You can change the impedance of a ground-plane antenna by changing the angle of the radials. Bending or sloping the radials downward to about a 45-degree angle will increase the impedance from approximately 35 ohms to approximately 50 ohms, reducing SWR. {br/}{br/}{image src='Fig G9-03.png'}

Answer 388

A: A ½-wavelength dipole antenna ½ wavelength or more above the ground radiates its signals in a bi-directional fashion with maximum radiation at a 90º angle to the antenna. This is called a “figure 8” radiation pattern. If the antenna is placed less than 1/2 wavelength above the ground, reflections from the ground will cause more of the antenna’s signal to be radiated at high vertical angles and the pattern becomes omnidirectional. {br/}{br/}{image src='Fig G9-04.png'}

Answer 389

C: As height is reduced below 1/2 wavelength the antenna pattern becomes almost omnidirectional, sending signals nearly equally in all compass directions.

Answer 390

C: In most installations, ground conductivity is inadequate to serve as the antenna’s ground plane, so an artificial ground screen must be made from wires placed along the ground near the base of the antenna. These radials are usually ¼ wavelength or longer. Depending on ground conductivity, 8, 16, 32 or more radials may be required to form an effective ground. The radial wires of a ground-mounted vertical antenna should be placed on the ground surface or buried a few inches below the surface.

Answer 391

B: As the antenna is lowered below ¼ wavelength above ground, the impedance steadily decreases to a very low value when placed directly on the ground.

Answer 392

A: The center of a ½-wavelength dipole is the location of the lowest feed point impedance, approximately 72 ohms in free space. At the ends of the dipole, feed point impedance is several thousand ohms. In between, feed point impedance increases steadily as the feed point is moved from the center towards the ends of the antenna.

Answer 393

A: {image src='G9B09.png'}

Answer 394

D: In free space, ½ wavelength in feet equals 492 divided by frequency in MHz. If you cut a piece of wire that length, however, you’ll find it is too long to resonate at the desired frequency. A resonant ½-wave dipole made of ordinary wire will be shorter than the free-space wavelength for several reasons. First, the physical thickness of the wire makes it look a bit longer electrically than it is physically. The lower the length-to-diameter (l/d) ratio of the wire, the shorter it will be when it is resonant. Second, the dipole’s height above ground also affects its resonant frequency. In addition, nearby conductors, insulation on the wire, the means by which the wire is secured to the insulators and to the feed line also affect the resonant length. For these reasons, a single universal formula for dipole length, such as the common 468/f, is not very useful. You should be start with a length near the free-space length and be prepared to trim the dipole to resonance using an SWR meter or antenna analyzer. The exam only requires that you identify an approximate resonant length for a dipole. Use the free-space length, calculated as 492 / f (in MHz), and select the closest choice. In this case, length (feet) = 492 / 14.250 = 34.5 feet, so select the closest value; 32 feet.

Answer 395

C: In free space, ½ wavelength in feet equals 492 divided by frequency in MHz. If you cut a piece of wire that length, however, you’ll find it is too long to resonate at the desired frequency. A resonant ½-wave dipole made of ordinary wire will be shorter than the free-space wavelength for several reasons. First, the physical thickness of the wire makes it look a bit longer electrically than it is physically. The lower the length-to-diameter (l/d) ratio of the wire, the shorter it will be when it is resonant. Second, the dipole’s height above ground also affects its resonant frequency. In addition, nearby conductors, insulation on the wire, the means by which the wire is secured to the insulators and to the feed line also affect the resonant length. For these reasons, a single universal formula for dipole length, such as the common 468/f, is not very useful. You should be start with a length near the free-space length and be prepared to trim the dipole to resonance using an SWR meter or antenna analyzer. The exam only requires that you identify an approximate resonant length for a dipole. Use the free-space length, calculated as 492 / f (in MHz), and select the closest choice. In this case, length (feet) = 492 / 3.550 = 139 ft. The closest value is 131 feet.

Answer 396

A: In free space, ½ wavelength in feet equals 492 divided by frequency in MHz. If you cut a piece of wire that length, however, you’ll find it is too long to resonate at the desired frequency. A resonant ½-wave dipole made of ordinary wire will be shorter than the free-space wavelength for several reasons. First, the physical thickness of the wire makes it look a bit longer electrically than it is physically. The lower the length-to-diameter (l/d) ratio of the wire, the shorter it will be when it is resonant. Second, the dipole’s height above ground also affects its resonant frequency. In addition, nearby conductors, insulation on the wire, the means by which the wire is secured to the insulators and to the feed line also affect the resonant length. For these reasons, a single universal formula for dipole length, such as the common 468/f, is not very useful. You should be start with a length near the free-space length and be prepared to trim the dipole to resonance using an SWR meter or antenna analyzer. The exam only requires that you identify an approximate resonant length for a dipole. Use the free-space length, calculated as 492 / f (in MHz), and select the closest choice. In this case, a 1/4-wavelength antenna would be half as long as a 1/2-wavelength antenna, so calculate length (feet) = 246 / 28.5 = 8.6 ft. The closest value is 8 feet.

Answer 397

A: Using larger diameter elements can increase the SWR bandwidth of a parasitic beam antenna, such as a Yagi antenna. The exact length of the elements becomes less critical when larger diameter elements are used.

Answer 398

B: A Yagi antenna consists of a driven element that is close to 1/2 wavelength long with one or more parasitic elements that help direct the radiated energy in one direction. Directors are parasitic elements that are mounted along the antenna's supporting boom in the preferred direction of radiation and reflectors are mounted in the opposite direction. {br/}{br/}{image src='Fig G9-05.png'}

Answer 399

B: In a typical three-element Yagi, the director is 95% the length of the driven element and is placed at the front of the driven element in the direction signals are to be transmitted and received. The reflector element is 105% of the length of the driven element and is placed to the rear. The director is normally the shortest element of a Yagi antenna. {br/}{br/}{image src='Fig G9-05.png'}

Answer 400

A: In a typical three-element Yagi, the director is 95% the length of the driven element and is placed at the front of the driven element in the direction signals are to be transmitted and received. The reflector element is 105% of the length of the driven element and is placed to the rear. The director is normally the shortest element of a Yagi antenna. {br/}{br/}{image src='Fig G9-05.png'}

Answer 401

A: As the boom length of a Yagi is increased and more elements are added, the directivity or gain of the antenna increases. Directivity has an advantage in that it concentrates the transmitted and received signals in the intended direction more than in other directions, thus minimizing interference and improving the signal-to-noise ratio of received signals.

Answer 402

C: A Yagi antenna provides gain or directivity. Directivity has an advantage in that it concentrates the transmitted and received signals in the intended direction more than in other directions. Directivity applies to receiving as well as transmitting, so the antenna picks up signals better from the desired direction and rejects signals coming from the sides or back of the antenna. This minimizes interference from stations in other directions. This is one important reason for using a Yagi antenna for HF operation, such as on the 20 meter band.

Answer 403

C: Using a directional antenna helps reduce interference in that it sends the signal in the intended direction rather than off to the side or behind. Most of the radiated signal is sent in the desired direction. This is called the major lobe of the antenna’s radiation pattern. A much smaller amount of the signal is radiated in other directions. If you measure the power radiated at the peak of the major lobe (or in the desired direction) and compare that with the power radiated in the exactly opposite direction, that is the antenna’s “front-to-back ratio.” {br/}{br/}{image src='Fig G9-06.png'}

Answer 404

D: A Yagi antenna radiates most of the signal in one direction. This is called the major lobe of the antenna’s radiation pattern. A much smaller amount of the signal is radiated in other directions. {br/}{br/}{image src='Fig G9-06.png'}

Answer 405

A: The maximum theoretical gain of a three-element Yagi antenna is 9.7 dBi. dBi means “decibels with respect to an isotropic antenna." An isotropic antenna is one that radiates equally in all possible directions.

Answer 406

D: All of these choices affect a Yagi antenna’s forward gain, front-to-back ratio, and SWR bandwidth. As you might imagine, adjusting an antenna design for the desired combination of these three important parameters can be a complicated procedure. Computer modeling programs greatly simplify this process.

Answer 407

A: A gamma match transforms the relatively low feed point impedance of a Yagi’s driven element (typically 25 ohms or less) to 50 ohms to match the characteristic impedance of common coaxial feed lines.

Answer 408

A: One major advantage of the gamma match is that the driven element does not have to be insulated from the antenna’s boom. This simplifies mounting the element and leads to a sturdier antenna.

Answer 409

A: All of the elements of a quad antenna are square-shaped loops. The entire driven element of a quad antenna is approximately a full wavelength, so each of the element’s four sides is approximately 1/4 wavelength long. {br/}{br/}{image src='Fig G9-07.png'}

Answer 410

B: A two-element quad (or delta loop) antenna has about the same gain as a three-element Yagi.

Answer 411

B: All of the elements of a quad antenna are square-shaped loops. The reflector element of a quad antenna is slightly more than a full wavelength (about 5% longer), so each of the four sides is slightly longer than 1/4 wavelength. {br/}{br/}{image src='Fig G9-07.png'}

Answer 412

D: Like the quad antenna, a delta-loop antenna uses loop elements that are approximately one wavelength long. The difference is that delta loop elements are triangle-shaped loops, rather than square. The gain of a delta loop is about the same as a quad antenna when the number of elements and spacing are the same. {br/}{br/}{image src='Fig G9-08.png'}

Answer 413

B: A delta-loop antenna has a driven element that is a triangle-shaped loop. It also uses a triangle-shaped loop reflector and sometimes one or more directors. The entire driven element of a delta-loop antenna is approximately a full wavelength, so each of the 3 sides is approximately 1/3 wavelength long. {br/}{br/}{image src='Fig G9-08.png'}

Answer 414

A: The polarization of signals radiated by a vertically-oriented 1-wavelength loop is determined by where the feed point is located. If the feed point is located at the top or bottom of the loop, the polarization of the radiated signal is horizontal. If the feed point is located on either side of the loop, the polarization of the radiated signal is vertical.

Answer 415

D: All of the elements of a quad antenna are square-shaped loops. The reflector element of a quad antenna is slightly more than a full wavelength (about 5% longer), so each of the four sides is slightly longer than 1/4 wavelength. {br/}{br/}{image src='Fig G9-07.png'}

Answer 416

B: “Stacking” two Yagis the proper distance apart combines their signals so that the forward gain of the resulting array is doubled, a gain of 3 dB.

Answer 417

D: NVIS, or Near Vertical Incidence Skywave, refers to a communications system that uses low, horizontally polarized antennas such as dipoles that radiate most of their signal at high vertical angles. These signals are then reflected back to Earth in a region centered on the antenna. NVIS allows stations to communicate within the skip zone for lower-angle sky wave propagation.

Answer 418

B: NVIS, or Near Vertical Incidence Skywave, refers to a communications system that uses low, horizontally polarized antennas such as dipoles that radiate most of their signal at high vertical angles. These signals are then reflected back to Earth in a region centered on the antenna. NVIS allows stations to communicate within the skip zone for lower-angle sky wave propagation.

Answer 419

D: NVIS must be mounted close to the ground so that the radiated signal is maximized at high vertical angles.

Answer 420

A: Traps consist of parallel LC circuits that act as electrical switches to isolate sections of the antenna at their resonant frequencies. At other frequencies, traps act as inductance or capacitance. This changes the antenna’s “electrical length” automatically, allowing it to operate on two or more bands.

Answer 421

D: The increase in gain for a vertical stack of Yagi antennas results from narrowing the vertical width of the main or major lobe of a single antenna’s radiation pattern. The narrower lobe results in stronger received signals and less received noise at angles away from the peak of the main lobe.

Answer 422

A: A log periodic antenna is designed to provide consistent gain and feed point impedance over a wide frequency range.

Answer 423

A: The name “log-periodic” refers to the ratio of length and spacing between adjacent elements of the antenna. By designing the antenna entirely in terms of ratios, the antenna’s performance becomes independent of frequency over a wide range

Answer 424

B: The Beverage antenna is used for receiving because it rejects noise and signals from unwanted directions, increasing the received signal-to-noise ratio for better copying ability. It is not used for transmitting because it is quite inefficient compared to most transmitting antennas.

Answer 425

B: Beverage antennas are most effective at frequencies of 7 MHz and below. This includes the amateur MF 160 meter band, as well as the lower HF bands of 80, 60, and 40 meters.

Answer 426

D: The typical Beverage antenna consists of a wire 1 wavelength or more long, supported from 6 to 10 feet above ground. It is terminated with a 300 to 1000-ohm resistor connected to a ground rod at the end of the antenna in the direction of preferred reception. It is highly directional, rejecting noise and signals from unwanted directions.

Answer 427

D: Multiband antennas by definition are designed to radiate well on several frequencies. Most HF amateur bands are harmonically-related, meaning their frequencies are integral multiples of each other--3.5, 7, 14, 21, and 28 MHz. While this is convenient in that one antenna can be used on separate bands, harmonics of a fundamental signal on, for example 7 MHz, will be radiated well by a multiband antenna on 14, 21, and 28 MHz.