Amateur Radio Practices Flashcards

Question

What effect can strong signals from nearby transmitters have on an antenna analyzer? A. Desensitization which can cause intermodulation products which interfere with impedance readings B. Received power that interferes with SWR readings C. Generation of harmonics which interfere with frequency readings D. All these choices are correct

Answer 1

B. Received power that interferes with SWR readings ## Footnote Antenna analyzers transmit a very weak signal and measures the SWR of that signal. A strong signal from a nearby transmitter can enter the antenna under test and be reflected to the analyzer, confusing the SWR reading. Hint: Super strong transmitter = SWR

Answer 2

C. Impedance of coaxial cable ## Footnote The antenna analyzer is a device that measures the input impedance of an antenna system. The Standing Wave Ratio (SWR) is a measure of impedance mismatch, which is why an antenna analyzer is used to figure it out. If you have an antenna with a known impedance, then you can use the antenna analyzer to figure out the impedance of an unknown or unmarked coaxial cable. Notice that none of the distractors have anything to do with impedance.

Answer 3

B. Bypass capacitor ## Footnote A bypass capacitor takes in extra noise or radio frequency interference (RFI) in the system and filters it out. A diode lets current flow in one direction. If a diode is forward-biased, it's letting current flow, and if it's reverse-biased, it's blocking it. Neither of these things would help remove RF interference. There is, apparently, such a thing as a bypass inductor, but it's not common, and it's hard to find any information about it, and it doesn't seem like it would help filter out RF interference.

Answer 4

C. Arcing at a poor electrical connection ## Footnote One source of interference could come from arcing at a poor electrical connection. Arcing because of poor wiring or a shorted component will cause fluctuations in the voltage passing that point. Out of the handbook "Arcing- Any spark or sustained arc creates radio noise over a wide range of frequencies and will interfere with both amateur and consumer reception. [G4C02]" For more info see Wikipedia: Electrical Arcing Mnemonic: Sparks fly everywhere

Answer 5

C. Distorted speech ## Footnote Hearing distorted speech on an audio device or telephone may occur if there is interference from a nearby single-sideband phone transmitter. Phones and stereos can sometimes pick up extra RF signals from nearby sources, just like your station receiver does, but the speech will be distorted.

Answer 6

A. On-and-off humming or clicking ## Footnote Telephones or audio devices can sometimes pick up interference RF signals from nearby transmission sources. If the interference is coming from a nearby CW transmitter, an on-and-off humming or clicking will be heard, which is a distorted version of the CW transmission. If the nearby interfering station was transmitting in SSB voice, distorted speech would be heard instead. CW stands for "continuous wave" transmissions. Originally communication was accomplished with a "straight key" and the operator, using "Morse Code" simply used the key to interrupt a continuous transmission into "dits" and "dahs", which explains why there will be clicking from CW interference.

Answer 7

D. The ground wire has high impedance on that frequency ## Footnote If you receive an RF burn when touching your equipment while transmitting on an HF band even though the equipment is connected to a ground rod, it may be because the ground wire has high impedance on that frequency. Remember impedance is a resistance to the flow of electrons, if the ground wire has high impedance, then it might have enough "apparent" resistance to make flowing through your equipment or your body a more efficient (lower resistance) path to ground. Silly hint: if you get a burn on your hand, it will impede your ability to use the hand.

Answer 8

C. High RF voltages on the enclosures of station equipment ## Footnote A resonant ground connection can cause high RF voltages on the enclosures of station equipment. Even though the equipment is grounded, if the ground wire is long enough it can actually resonate on the frequency you are using to transmit. When this happens, instead of acting to remove extra current, the ground wire gains high impedance, and so blocks the flow of electrons to the ground state. This means your enclosure, equipment or even body can become a more efficient path to ground, and conduct high RF voltages. Hint: [R]esonant ground = high [R]F

Answer 9

A. A soldered joint will likely be destroyed by the heat of a lightning strike ## Footnote Solder melts at such a low temperature compared to the incredible heat produced by a lightning strike that soldered joints would melt instantly and be destroyed. In situations where lightning strikes are more likely (like an antenna tower) ground clamps are the way to go.

Answer 10

A. Place a ferrite choke on the cable ## Footnote RF interference caused by common-mode current on an audio cable can be reduced by placing a ferrite bead around the cable. The ferrite bead, which can also be called a ferrite choke among other names, is used as a device to reduce noise in audio cables because of the high dissipation qualities of the ferrite material.

Answer 11

D. Bond equipment enclosures together ## Footnote A ground loop in your circuits can be avoided by connecting all of the ground conductors to a single point. A ground loop, or extra current path, is usually caused by components that are not designed or wired correctly. Loops can cause noise and interference. Keeping all wiring in direct paths, and especially connecting all of your ground conductors to a single point, help to keep loops from being formed.

Answer 12

A. You receive reports of “hum” on your station’s transmitted signal ## Footnote If stations that are receiving your communications report back to you that they are hearing a "hum" on your station's transmitted signal, you may have a ground loop somewhere in your station. This unwanted noise caused by picking up distortion from magnetic field voltages or from improper connections can be remedied by connecting all of your ground conductors to a single point.

Answer 13

C. Bonding all equipment enclosures together ## Footnote Just as you would tie all of your radio grounds together to prevent things such as ground loops, you want to bond all your radios together as well. Not bonding radios together can result in potential differences being present between them. Potential differences often result in high voltages being present on certain pieces of the radios, such as, a metal microphone piece, or even the radio itself.

Answer 14

D. It ensures that hazardous voltages cannot appear on the chassis ## Footnote It is good practice when setting up your station to make sure that you have grounded any equipment with a metal chassis. Excess voltage can be caught in the metal housing if there is a short within the equipment or wiring. Proper grounding ensures that you will not have a SHOCKING experience when you touch your equipment due to hazardous voltages on the chassis. Hint: A "metal enclosure" houses the "chassis".

Answer 15

A. Increase the apparent loudness of transmitted voice signals ## Footnote The primary purpose of a speech processor as used in modern transceivers is to increase the intelligibility of transmitted phone signals during poor conditions. The speech processor brings up the power of low level parts of phone or voice signals while not changing the high level parts of the signal. This effectively brings up the average signal power to a more even and understandable level, but with the benefit of not increasing the peak envelope power.

Answer 16

B. It increases average power ## Footnote The speech processor affects transmitted phone signals such as single sideband, by increasing the average power. The processor increases the power of low level signals, but not those of higher level signals. This raises the average signal level and makes the communication more intelligible. Another benefit of using the speech processor is that it raises the average power in such a way that the Peak Envelope Power is not increased. Processing even SSB Speech "Increases average power" of all speech.

Answer 17

D. All these choices are correct ## Footnote All of the choices listed are correct as results of an incorrectly adjusted speech processor. A speech processor modifies the signal by increasing the lower power parts of the signal to a higher average level without raising the upper level tones. Over or under adjusting this processor can cause various forms of distortion. It can bring up low level background noise (such as fans, background voices, machine noises) along with the low end range of your voice signal. Overprocessing can also distort your speech or overdrive the transmitter output causing "splatter" signals If you incorrectly adjust some speech then "ALL" speech gets messed up.

Answer 18

C. Received signal strength ## Footnote The signal strength measurements are related to the "S" or "strength" part of the RST code for reporting signal quality. The scale uses S units on a subjective scale of S1 to S9 (see RST Code). The meter is not always accurately calibrated, but it tries to make the S reading less subjective by relating it to a logarithmic scale of decibel units. A change of one S unit indicates a four times increase or decrease in signal power, this corresponds to a 6 decibel change.

Answer 19

D. It is 100 times more powerful ## Footnote An S meter reading of 20 dB over S9 is 100 times stronger than an S9 signal, assuming a properly calibrated S meter. The S meter measures the signal strength by trying to relate the subjective S1-S9 scale with a logarithmic scale of decibel units, which is a powers of 10 scale. From S1 through S9, a one unit change in S unit corresponds to a 4 fold increase in power which is a change of 6 dB on the logarithmic scale. Above S9 the scale continues as 10 decibel units over S9. Following the logarithmic scale, 10 dB over S9 is 10 (101) times stronger, 20 dB over S9 is 100 (102) times stronger. Also remember every 3 dB is ≈2× power, so 20 dB is between 6 and 7 doublings. 203≈6.66, which we can confirm with: 26.66=101 For more info see Wikipedia: S meter, RST Scale, Decibel Silly hint: S(9) x S(9) = S(81) 81 + 20 dB = 101 101 is closest to the answer.

Answer 20

A. 6 dB ## Footnote From Wikipedia: The term S unit refers to the amount of signal strength required to move an S meter indication from one marking to the next. The answer is 6 dB which you really just need to remember. Remember that a 3 dB change is double (or half, depending on the direction), so S2 is four times (4x) as powerful as S1, and S3 is four times stronger than S2, etc. More detail: Each marker on a typical S meter (one which follows the IARU Region 1 Technical Recommendation R.1) is 6 dB higher than the last, with the highest marking (S9) corresponding to 50 μV at the input of the receiver. Hint: An S is closer in shape to a 6 than any of the other answers.

Answer 21

C. Approximately 4 times ## Footnote The power output of a transmitter must be raised approximately 4 times to change the S-meter reading on a distant receiver from S8 to S9. Thus for the reading on the scale to increase by 1 S unit indicates that the signal strength has increased by four times, which corresponds to approximately a change of 6 decibels on a logarithmic scale. A mnemonic - An S-meter Steps by Six db (which is a 4x change)

Answer 22

C. 7.175 MHz to 7.178 MHz ## Footnote The bandwidth from 7.175 to 7.178 MHz is the frequency range occupied by a 3 kHz LSB signal when the displayed carrier frequency is set to 7.178 MHz. Most radios show the frequency of a single sideband transmission as the frequency of the carrier signal. An SSB signal with a bandwidth of 3 kHz using the lower sideband (LSB) would be the range from 3 KHz below the carrier frequency up to the carrier frequency. In the same manner, the same signal using the upper sideband (USB) would use the range from the carrier frequency to 3 KHz above the carrier frequency. Easy Hint: LOWER sideband goes DOWN, and the correct answer is the only answer that ends in 7.178 MHz.

Answer 23

B. 14.347 MHz to 14.350 MHz ## Footnote A USB signal with a bandwidth of 3 kHz displayed at a frequency of 14.347 MHz, uses the range from the 14.347 MHz to 14.350 MHz. Most radios show the frequency of an SSB transmission as the frequency of the signal carrier. An upper sideband bandwidth ranges from the carrier frequency level for the range of 1 bandwidth above that number: When adding frequencies together, make sure both frequencies are using the same units: Range=(14.347 MHz to 14.347 MHz+3 kHz)=(14.347 MHz to 14.347 MHz+0.003 MHz)=(14.347 MHz to 14.350 MHz)

Answer 24

A. At least 3 kHz above the edge of the segment ## Footnote A 3 kHz wide LSB signal on the 40 meter General Class phone segment should have a displayed carrier frequency no closer than 3 kHz above the lower edge of the segment. A lower sideband (LSB) transmission uses the width of the band BELOW the displayed frequency. An amateur operator must take care that the entire portion of the transmitted signal is within granted class privileges. You cannot have an LSB signal with a displayed frequency at exactly the lower edge, because the LSB transmission would actually be outside the permitted range! You must keep the displayed frequency at least 1 bandwidth from the edge of the band segment.

Answer 25

B. At least 3 kHz below the edge of the band ## Footnote When using a 3 kHz wide USB signal, your displayed carrier frequency should be no closer than 3 kHz below the upper edge of the band. An upper sideband transmission actually uses the frequency portion from the carrier frequency to 1 bandwidth ABOVE that frequency. An amateur operator must make sure that the entire signal is within the band privileges. To keep a 3 KHz USB signal within range, a carrier frequency of no closer than the bandwidth below the upper range may be used.

Answer 26

C. To electrically lengthen a physically short antenna ## Footnote A "capacitance hat" is a device on the end of a mobile antenna which acts to electrically lengthen a physically short antenna. The device, usually made up of a ring, or an arrangement of rods, is used on the top of the antenna. The device increases the capacitance of the antenna, which causes it to act electrically "longer." SILLY HINT: A "top hat" makes a short person look taller/longer.

Answer 27

D. To reduce RF voltage discharge from the tip of the antenna while transmitting ## Footnote A "corona ball" on a HF mobile antenna is used to reduce high voltage discharge from the tip of the antenna. The sharp tipped mobile antenna can discharge extra voltage that builds up as an electrical arc or coronal discharge. The corona ball device reduces the chance of forming such arcs. Study Tip: Corona (virus) is a *transmitting" pandemic. Associate Corona with the word transmitting which appears in the correct answer. Reduce corona voltage/hysteria by putting a ball/cap on it. Definitely want to REDUCE covid.

Answer 28

A. To the battery using heavy-gauge wire ## Footnote The best direct, fused power connection for a 100-watt HF mobile installation is a connection directly to the battery using heavy-gauge wire. This ensures the radio can handle the high current needed without causing voltage drops. Avoid using the auxiliary outlet, as it cannot handle the required power. For setups with multiple power connections, it’s also a good idea to use a bus bar, preferably a radio/avionics bus bar, to safely distribute power to additional devices. This helps keep wiring organized and prevents overloading the battery terminals. When connecting directly to the battery, take precautions to avoid corrosion by using a protective sealant on the terminals, and ensure the wiring is safely routed through grommets or protective sheaths to avoid damage. Also, fuses should be installed as close to the battery as possible on both the positive and negative leads.

Answer 29

B. The socket’s wiring may be inadequate for the current drawn by the transceiver ## Footnote It is best NOT to draw the DC power for a 100-watt HF transceiver from an automobile's auxiliary power socket because the socket's wiring may be inadequate for the current being drawn by the transceiver. Instead, the unit should be powered by connecting heavy gauge wire leads to the battery terminals, with fuses on the leads located as close to the battery as possible.

Answer 30

C. Efficiency of the electrically short antenna ## Footnote Keyword: most Picket fencing relates generally to weak FM signals. While there are FM operations on the 10-meter band, this would not impact any other HF band. The wire gauge of the transceiver's power line could impact maximum power output, but this is a variable highly in the control of the radio owner. There isn't a FCC rule limiting mobile output power. HF antennas are often electrically short, and are highly inefficient. This is an impact on all HF bands.

Answer 31

C. Operating bandwidth may be very limited ## Footnote One disadvantage of using a shortened mobile antenna as opposed to a full size antenna is that operating bandwidth may be very limited. The fractional wave electrically short antennas have low impedances at the feed point and very narrow frequency ranges. Unfortunately, it just is not practical or safe to attach the length of antenna required for efficient transmitting, especially at HF frequencies. Key: "limited antenna" a.k.a mobile, limited bandwith

Answer 32

D. All these choices are correct ## Footnote Yes, the alternator ( battery charging system) can give off a whine. Yes, the fuel pump ( fuel delivering system) can give off a similar whine. Yes, the control computer can give off stray rf interference. So all of these choices are, indeed correct. All I can say is, modern vehicles were not designed for the average ham.

Answer 33

A. Series-parallel ## Footnote Solar cells provide DC power similar to a battery. Each solar cell provides a specific amount of power based on light conditions. Desired output voltage is generated by connecting cells in series (like multiple AAs in a flashlight). Desired current is generated by connecting banks of solar cells in parallel. Thus, Series-parallel is the correct answer. The distractors shunt and bypass divert power away from components. The distractor Full-wave bridge is for converting AC to DC, but solar generates DC power.

Answer 34

B. 0.5 VDC ## Footnote The current standard modern, well-illuminated (full sun exposure) photovoltaic cell has an approximate open-circuit voltage of 0.5 Volts DC. These cells may also be known as solar or photoelectric cells. The maximum current that a photovoltaic cell can provide is dependent on the total surface area of the cell. Individual standard cells may be arranged together to form solar panels for larger power requirements.

Answer 35

B. To prevent discharge of the battery through the panel during times of low or no illumination ## Footnote A diode only lets current flow in one direction. The direction you want if you're collecting solar energy is from the solar panel to the battery. The diode will prevent the energy from going in the other direction when the battery has more energy than the solar panel (during the night or other periods of low light). Silly Hint: A Diode is Directional, preventing a change of direction of current, and therefore preventing Discharge, all words beginning with D-I-. Note: When a Zener diode is used to control voltage it does so with reverse polarity compared to a diode that would prevent energy from going to the panel. A Zener diode limits the voltage, but not the current nor the power.

Answer 36

D. The solar panel must have a charge controller ## Footnote A charge controller limits the rate at which electric current is added to or drawn from electric batteries to protect against electrical overload, overcharging, and may protect against overvoltage. This prevents conditions that reduce battery performance or lifespan and may pose a safety risk. Without a charge controller, batteries can be damaged by incoming power, and could also leak power back to the solar panels when the sun isn’t shining. SILLY HINT: For those that work out at a gym lifting weights, when "lifting iron" (lithium iron), you need to do so in a very "controlled" (controller) manner. The correct answer is the only one with the word controller in it.

Amateur Radio Practices Flashcards

Station configuration and operation