Amateur Radio Practices Flashcards
Station configuration and operation
What is the purpose of the notch filter found on many HF transceivers?
A. To restrict the transmitter voice bandwidth
B. To reduce interference from carriers in the receiver passband
C. To eliminate receiver interference from impulse noise sources
D. To remove interfering splatter generated by signals on adjacent frequencies
B. To reduce interference from carriers in the receiver passband
The “notch filter” found on many HF transceivers is to reduce interference from carriers in the receiver passband. The “notch” refers to a narrow area of frequency interference that you want to get rid of, while being able to maintain the quality of the nearby signal you want to keep.
General hint for most questions like this one: “WE HATE INTERFERENCE”
What is the benefit of using the opposite or “reverse” sideband when receiving CW?
A. Interference from impulse noise will be eliminated
B. More stations can be accommodated within a given signal passband
C. It may be possible to reduce or eliminate interference from other signals
D. Accidental out-of-band operation can be prevented
C. It may be possible to reduce or eliminate interference from other signals
When working with CW signals on a typical HF transceiver it may be beneficial to select the opposite or “reverse” sideband, as this may make it possible to reduce or eliminate interference from other signals. This method will work with CW, because it transmits just tones of dots and dashes. It won’t work with a voice/phone signal because it would flip the speech pattern, making it impossible to understand.
HINT: “REverse” in the question; “REduce” in the correct answer.
How does a noise blanker work?
A. By temporarily increasing received bandwidth
B. By redirecting noise pulses into a filter capacitor
C. By reducing receiver gain during a noise pulse
D. By clipping noise peaks
C. By reducing receiver gain during a noise pulse
The noise blanker works on eliminating the annoying sound of repetitive pulses such that are heard with automotive ignition energy, some diesel engines, or the famous Russian ‘Woodpecker’ radar radio frequency emissions.
https://en.wikipedia.org/wiki/Noise_blanker
Noise Blanket “Blanker” works to reduce cold “Receiver gain” during a cold front “Noise pulse”
What is the effect on plate current of the correct setting of a vacuum-tube RF power amplifier’s TUNE control?
A. A pronounced peak
B. A pronounced dip
C. No change will be observed
D. A slow, rhythmic oscillation
B. A pronounced dip
A pronounced dip or drop in the reading on the plate current meter of a vacuum tube RF amplifier shows that you have correct adjustment of the plate tuning control. This dip happens when the impedance is matched at the right frequency.
Note: It is kind of like “zero beating” a CW signal, with the reading/mismatch being higher on either side of the correct level, and reaching zero when frequencies are matched to each other.
Mnemonics:
To “peak the grid, dip the plate”.
Keep tuning until you stop wasting electricity (low current).
What is plate current?
Plate Current is the amperage that flows across a tube from the cathode to the plate. In the case of an audio tube, the control grid and screen grid mediate the amount of current that flows from cathode to plate.
Why is automatic level control (ALC) used with an RF power amplifier?
A. To balance the transmitter audio frequency response
B. To reduce harmonic radiation
C. To prevent excessive drive
D. To increase overall efficiency
C. To prevent excessive drive
The ALC avoids feeding too much power to the amplifier. Too much power can cause the amplifier to overdrive, which causes distortion in the signal and extraneous interferences.
hint: Vehicle Automatic Traction Control helps to “Prevent excessive drive”
What is the purpose of an antenna tuner?
A. Reduce the SWR in the feed line to the antenna
B. Reduce the power dissipation in the feedline to the antenna
C. Increase power transfer from the transmitter to the feed line
D. All these choices are correct
C. Increase power transfer from the transmitter to the feed line
Maximum power transfer occurs when the antenna system (antenna plus transmission line) has the same impedance as the transmitter.
If the antenna system has too much capacitance, you can offset that by adding inductance. If it has too much inductance, you can offset that by adding capacitance. The antenna tuner adds the necessary capacitance and/or inductance so the antenna system and tuner appear to the transmitter as a perfect match.
An antenna tuner is only necessary when there’s a mismatch between the transmitter and antenna system. If the antenna and transmission line have the same impedance as the transmitter, there is no need for an antenna tuner.
Most amateur radio transmitters have an impedance of 50 ohms.
Hint: The answer is the only one that does not have the word antenna!
What happens as a receiver’s noise reduction control level is increased?
A. Received signals may become distorted
B. Received frequency may become unstable
C. CW signals may become severely attenuated
D. Received frequency may shift several kHz
A. Received signals may become distorted
As the noise reduction control is made to be more aggressive, additional parts of the signal become progressively targeted. Some of these parts are valuable to the quality of the audio.
What is the correct adjustment for the LOAD or COUPLING control of a vacuum tube RF power amplifier?
A. Minimum SWR on the antenna
B. Minimum plate current without exceeding maximum allowable grid current
C. Highest plate voltage while minimizing grid current
D. Desired power output without exceeding maximum allowable plate current
D. Desired power output without exceeding maximum allowable plate current
The load or coupling control of a vacuum tube RF power amplifier should be adjusted so that it is at the maximum power output usable without exceeding the maximum allowable plate current. The Load control for the RF power amplifier should be adjusted alternately with the Tune control adjusting the plate current until the highest matching amplifier power output level can be found without overloading the plate current.
HINT: both the question and answer use the word “power”
What is the purpose of delaying RF output after activating a transmitter’s keying line to an external amplifier?
A. To prevent key clicks on CW
B. To prevent transient overmodulation
C. To allow time for the amplifier to switch the antenna between the transceiver and the amplifier output
D. To allow time for the amplifier power supply to reach operating level
C. To allow time for the amplifier to switch the antenna between the transceiver and the amplifier output
When the keying line of a transmitter is activated, it signals the external amplifier to start transmitting. However, there is a slight delay introduced to ensure that the amplifier has enough time to switch the antenna connection between the transceiver and the amplifier output.
While it is true that it can take the amplifier power supply some brief time to reach operating level the worst case there is for the signal to be a bit off at first; whereas if the antenna is fully switched over or particularly if there is any way for energy to leak from the transmitter into the receiver then it could cause actual damage to the transceiver.
What is the function of an electronic keyer?
A. Automatic transmit/receive switching
B. Automatic generation of dots and dashes for CW operation
C. To allow time for switching the antenna from the receiver to the transmitter
D. Computer interface for PSK and RTTY operation
B. Automatic generation of dots and dashes for CW operation
Why should the ALC system be inactive when transmitting AFSK data signals?
A. ALC will invert the modulation of the AFSK mode
B. The ALC action distorts the signal
C. When using digital modes, too much ALC activity can cause the transmitter to overheat
D. All these choices are correct
B. The ALC action distorts the signal
Improper action of ALC distorts the signal and can cause spurious emissions
The Automatic Level Control (ALC) makes sure signals do not clip by compressing them. If you’ve dealt with audio production, this is a similar process to dynamic compression. The compressed signal sounds similar to the original signal, but it usually comes with distortion.
This distortion is acceptable in voice communication, but in digital modes, compression may generate emissions not intended by the pure signal from your computer.
Hint: Wrong Action Distorts
Which of the following is a common use of the dual-VFO feature on a transceiver?
A. To allow transmitting on two frequencies at once
B. To permit full duplex operation – that is, transmitting and receiving at the same time
C. To transmit on one frequency and listen on another
D. To improve frequency accuracy by allowing variable frequency output (VFO) operation
C. To transmit on one frequency and listen on another
SILLY HINT: In a “Dual” relationship, one person needs to listen (receiver), while the other partner talks (transmitter) and for best communication either person should not try to talk and listen at the same time.
SILLY HINT2: It’s “common use” - we don’t commonly use full duplex, but we do “commonly” transmit and then receive.
VFO = variable frequency oscillator
What is the purpose of using a receive attenuator?
A. To prevent receiver overload from strong incoming signals
B. To reduce the transmitter power when driving a linear amplifier
C. To reduce power consumption when operating from batteries
D. To reduce excessive audio level on strong signals
A. To prevent receiver overload from strong incoming signals
Attenuators are used in HF transceivers to reduce signal overload due to strong incoming signals. An attenuator acts as the opposite of an amplifier. Its purpose is to reduce the power or amplitude of a signal rather than increasing it, while still keeping the signal strong. This keeps the signal from having the distortion that would be experienced with too much incoming signal energy. Think of the attenuator as a downward volume control for the signal power.
Memory device: Receive attenuator prevents receiver overload.
Attenuation means to reduce; overload means to overburden or strain. When a signal is too strong you can attenuate the signal to prevent overloading the receiver.
What item of test equipment contains horizontal and vertical channel amplifiers?
A. An ohmmeter
B. A signal generator
C. An ammeter
D. An oscilloscope
D. An oscilloscope
The oscilloscope is the item of test equipment which contains horizontal and vertical channel amplifiers. This allows the equipment to evaluate wave forms of RF signals, and observe changes to the signal with varying signal voltages by plotting values on the X (horizontal) and Y (vertical) axes over time.
Which of the following is an advantage of an oscilloscope versus a digital voltmeter?
A. An oscilloscope uses less power
B. Complex impedances can be easily measured
C. Greater precision
D. Complex waveforms can be measured
D. Complex waveforms can be measured
Both the digital voltmeter and oscilloscope can display different values of signal voltage, but complex waveforms can be hard to measure with a digital voltmeter—it’s all just numbers. With a complex waveform often all you really want is to find a particular feature (like a peak), and that can be much easier by eyeballing it.
HINT: Oscilloscope is a complex word
“Oscilloscopes” show “Complex waves”
Which of the following is the best instrument to use for checking the keying waveform of a CW transmitter?
A. An oscilloscope
B. A field strength meter
C. A sidetone monitor
D. A wavemeter
A. An oscilloscope
An Oscilloscope is used to measure oscillations in an electrical signal – in other words, it shows you the waveform of the signal. The keying waveform of a CW transmitter is the visual representation of the tone transmitted by the transmitter when you press the key, which can be seen on the oscilloscope screen.
What signal source is connected to the vertical input of an oscilloscope when checking the RF envelope pattern of a transmitted signal?
A. The local oscillator of the transmitter
B. An external RF oscillator
C. The transmitter balanced mixer output
D. The attenuated RF output of the transmitter
D. The attenuated RF output of the transmitter
The attenuated RF output of the transmitter is connected to the vertical input of an oscilloscope when checking the RF envelope pattern of a transmitted signal. This allows you to check for signal distortions.
For more info see Wikipedia: Oscilloscope
**Memory tip: Output in the answer corresponds to Input in the question. ** KC3TGS
HINT: RF INPUT is in the question, RF OUTPUT is in the correct answer. KF4TYA
Why do voltmeters have high input impedance?
A. It improves the frequency response
B. It allows for higher voltages to be safely measured
C. It improves the resolution of the readings
D. It decreases the loading on circuits being measured
D. It decreases the loading on circuits being measured
Impedance is the measure of opposition to the flow of current. High input impedance is desired for a voltmeter because it limits, or decreases that loading on circuits being measured. Because of this the voltmeter only has to draw a very small amount of current from the circuit to be tested, and doesn’t interfere with the normal flow and operation.
What is an advantage of a digital multimeter as compared to an analog multimeter?
A. Better for measuring computer circuits
B. Less prone to overload
C. Higher precision
D. Faster response
C. Higher precision
A digital voltmeter has an advantage over an analog meter because it has better precision for most uses. Digital voltmeters are easy to read if you are looking for a specific number level rather than trying to interpret the needle position on an analog scale. The analog meter may be more useful, however if you are looking for general up/down trends with being able to see the needle move in either direction, rather than focusing in on a specific value.
What signals are used to conduct a two-tone test?
A. Two audio signals of the same frequency shifted 90 degrees
B. Two non-harmonically related audio signals
C. Two swept frequency tones
D. Two audio frequency range square wave signals of equal amplitude
B. Two non-harmonically related audio signals
A two-tone test uses two non-harmonically related audio signals to test the linearity of signal amplitude in an SSB transmission. The two tones of equal power are put into the microphone input and the waveforms are examined for linearity using an oscilloscope.
What transmitter performance parameter does a two-tone test analyze?
A. Linearity
B. Percentage of suppression of the carrier and undesired sideband for SSB
C. Percentage of frequency modulation
D. Percentage of carrier phase shift
A. Linearity
A two-tone test measures the linearity of an SSB signal.
A perfectly linear transmitter would produce those two tones—and only those two tones.
The more non-linear the transmitter, the more harmonics are generated, producing additional signal content at frequencies other than the two input tones.
The test itself consists of sending two tones that are not harmonically related into the transmitter. The tones are produced with equal power levels, so the only variable is frequency. The output can then be examined using an oscilloscope or spectroscope to see what other signals are being produced at other frequencies.
When is an analog multimeter preferred to a digital multimeter?
A. When testing logic circuits
B. When high precision is desired
C. When measuring the frequency of an oscillator
D. When adjusting circuits for maximum or minimum values
D. When adjusting circuits for maximum or minimum values
When adjusting a circuit connected to an analog meter, you can see the indicator moving to a higher or lower reading - it’s moving up or down.
When you’re adjusting for a maximum or minimum value, you only have to look at whether it’s moving up or down - you don’t have to interpret a digital display of a number to get a sense of whether it’s increasing or decreasing.
Which of the following can be determined with a directional wattmeter?
A. Standing wave ratio
B. Antenna front-to-back ratio
C. RF interference
D. Radio wave propagation
A. Standing wave ratio
A directional wattmeter is used to determine the standing wave ratio, which is the relationship between the forward and reflected power.
Its easy to determine the “Direction” of a wave if you are “Standing in the wave”
Oversimplification: Most SWR meters will tell you your forward watts and your reverse/reflected watts, in both directions.
Which of the following must be connected to an antenna analyzer when it is being used for SWR measurements?
A. Receiver
B. Transmitter
C. Antenna and feed line
D. All these choices are correct
C. Antenna and feed line
Both the antenna and feed line must be connected to an antenna analyzer when it is being used for SWR (standing wave ratio) measurements. This device helps to measure the effeciency of your antenna setup.
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
B. Received power that interferes with SWR readings
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
Which of the following can be measured with an antenna analyzer?
A. Front-to-back ratio of an antenna
B. Power output from a transmitter
C. Impedance of coaxial cable
D. Gain of a directional antenna
C. Impedance of coaxial cable
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.
Which of the following might be useful in reducing RF interference to audio frequency circuits?
A. Bypass inductor
B. Bypass capacitor
C. Forward-biased diode
D. Reverse-biased diode
B. Bypass capacitor
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.
Which of the following could be a cause of interference covering a wide range of frequencies?
A. Not using a balun or line isolator to feed balanced antennas
B. Lack of rectification of the transmitter’s signal in power conductors
C. Arcing at a poor electrical connection
D. Using a balun to feed an unbalanced antenna
C. Arcing at a poor electrical connection
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
What sound is heard from an audio device experiencing RF interference from a single sideband phone transmitter?
A. A steady hum whenever the transmitter is on the air
B. On-and-off humming or clicking
C. Distorted speech
D. Clearly audible speech
C. Distorted speech
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.
What sound is heard from an audio device experiencing RF interference from a CW transmitter?
A. On-and-off humming or clicking
B. A CW signal at a nearly pure audio frequency
C. A chirpy CW signal
D. Severely distorted audio
A. On-and-off humming or clicking
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.
What is a possible cause of high voltages that produce RF burns?
A. Flat braid rather than round wire has been used for the ground wire
B. Insulated wire has been used for the ground wire
C. The ground rod is resonant
D. The ground wire has high impedance on that frequency
D. The ground wire has high impedance on that frequency
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.
What is a possible effect of a resonant ground connection?
A. Overheating of ground straps
B. Corrosion of the ground rod
C. High RF voltages on the enclosures of station equipment
D. A ground loop
C. High RF voltages on the enclosures of station equipment
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
Why should soldered joints not be used in lightning protection ground connections?
A. A soldered joint will likely be destroyed by the heat of a lightning strike
B. Solder flux will prevent a low conductivity connection
C. Solder has too high a dielectric constant to provide adequate lightning protection
D. All these choices are correct
A. A soldered joint will likely be destroyed by the heat of a lightning strike
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.
Which of the following would reduce RF interference caused by common-mode current on an audio cable?
A. Place a ferrite choke on the cable
B. Connect the center conductor to the shield of all cables to short circuit the RFI signal
C. Ground the center conductor of the audio cable causing the interference
D. Add an additional insulating jacket to the cable
A. Place a ferrite choke on the cable
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.
How can the effects of ground loops be minimized?
A. Connect all ground conductors in series
B. Connect the AC neutral conductor to the ground wire
C. Avoid using lock washers and star washers when making ground connections
D. Bond equipment enclosures together
D. Bond equipment enclosures together
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.
What could be a symptom caused by a ground loop in your station’s audio connections?
A. You receive reports of “hum” on your station’s transmitted signal
B. The SWR reading for one or more antennas is suddenly very high
C. An item of station equipment starts to draw excessive amounts of current
D. You receive reports of harmonic interference from your station
A. You receive reports of “hum” on your station’s transmitted signal
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.
What technique helps to minimize RF “hot spots” in an amateur station?
A. Building all equipment in a metal enclosure
B. Using surge suppressor power outlets
C. Bonding all equipment enclosures together
D. Placing low-pass filters on all feed lines
C. Bonding all equipment enclosures together
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.
Why must all metal enclosures of station equipment be grounded?
A. It prevents a blown fuse in the event of an internal short circuit
B. It prevents signal overload
C. It ensures that the neutral wire is grounded
D. It ensures that hazardous voltages cannot appear on the chassis
D. It ensures that hazardous voltages cannot appear on the chassis
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”.
What is the purpose of a speech processor in a transceiver?
A. Increase the apparent loudness of transmitted voice signals
B. Increase transmitter bass response for more natural-sounding SSB signals
C. Prevent distortion of voice signals
D. Decrease high-frequency voice output to prevent out-of-band operation
A. Increase the apparent loudness of transmitted voice signals
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.
How does a speech processor affect a single sideband phone signal?
A. It increases peak power
B. It increases average power
C. It reduces harmonic distortion
D. It reduces intermodulation distortion
B. It increases average power
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.
What is the effect of an incorrectly adjusted speech processor?
A. Distorted speech
B. Excess intermodulation products
C. Excessive background noise
D. All these choices are correct
D. All these choices are correct
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.
What does an S meter measure?
A. Carrier suppression
B. Impedance
C. Received signal strength
D. Transmitter power output
C. Received signal strength
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.
How does a signal that reads 20 dB over S9 compare to one that reads S9 on a receiver, assuming a properly calibrated S meter?
A. It is 10 times less powerful
B. It is 20 times less powerful
C. It is 20 times more powerful
D. It is 100 times more powerful
D. It is 100 times more powerful
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.
How much change in signal strength is typically represented by one S unit?
A. 6 dB
B. 12 dB
C. 15 dB
D. 18 dB
A. 6 dB
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.
How much must the power output of a transmitter be raised to change the S meter reading on a distant receiver from S8 to S9?
A. Approximately 1.5 times
B. Approximately 2 times
C. Approximately 4 times
D. Approximately 8 times
C. Approximately 4 times
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)
What frequency range is occupied by a 3 kHz LSB signal when the displayed carrier frequency is set to 7.178 MHz?
A. 7.178 MHz to 7.181 MHz
B. 7.178 MHz to 7.184 MHz
C. 7.175 MHz to 7.178 MHz
D. 7.1765 MHz to 7.1795 MHz
C. 7.175 MHz to 7.178 MHz
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.
What frequency range is occupied by a 3 kHz USB signal with the displayed carrier frequency set to 14.347 MHz?
A. 14.347 MHz to 14.647 MHz
B. 14.347 MHz to 14.350 MHz
C. 14.344 MHz to 14.347 MHz
D. 14.3455 MHz to 14.3485 MHz
B. 14.347 MHz to 14.350 MHz
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)
How close to the lower edge of a band’s phone segment should your displayed carrier frequency be when using 3 kHz wide LSB?
A. At least 3 kHz above the edge of the segment
B. At least 3 kHz below the edge of the segment
C. At least 1 kHz below the edge of the segment
D. At least 1 kHz above the edge of the segment
A. At least 3 kHz above the edge of the segment
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.
How close to the upper edge of a band’s phone segment should your displayed carrier frequency be when using 3 kHz wide USB?
A. At least 3 kHz above the edge of the band
B. At least 3 kHz below the edge of the band
C. At least 1 kHz above the edge of the segment
D. At least 1 kHz below the edge of the segment
B. At least 3 kHz below the edge of the band
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.
What is the purpose of a capacitance hat on a mobile antenna?
A. To increase the power handling capacity of a whip antenna
B. To reduce radiation resistance
C. To electrically lengthen a physically short antenna
D. To lower the radiation angle
C. To electrically lengthen a physically short antenna
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.
What is the purpose of a corona ball on an HF mobile antenna?
A. To narrow the operating bandwidth of the antenna
B. To increase the “Q” of the antenna
C. To reduce the chance of damage if the antenna should strike an object
D. To reduce RF voltage discharge from the tip of the antenna while transmitting
D. To reduce RF voltage discharge from the tip of the antenna while transmitting
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.
Which of the following direct, fused power connections would be the best for a 100-watt HF mobile installation?
A. To the battery using heavy-gauge wire
B. To the alternator or generator using heavy-gauge wire
C. To the battery using insulated heavy duty balanced transmission line
D. To the alternator or generator using insulated heavy duty balanced transmission line
A. To the battery using heavy-gauge wire
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.
Why should DC power for a 100-watt HF transceiver not be supplied by a vehicle’s auxiliary power socket?
A. The socket is not wired with an RF-shielded power cable
B. The socket’s wiring may be inadequate for the current drawn by the transceiver
C. The DC polarity of the socket is reversed from the polarity of modern HF transceivers
D. Drawing more than 50 watts from this socket could cause the engine to overheat
B. The socket’s wiring may be inadequate for the current drawn by the transceiver
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.
Which of the following most limits an HF mobile installation?
A. “Picket fencing”
B. The wire gauge of the DC power line to the transceiver
C. Efficiency of the electrically short antenna
D. FCC rules limiting mobile output power on the 75-meter band
C. Efficiency of the electrically short antenna
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.
What is one disadvantage of using a shortened mobile antenna as opposed to a full-size antenna?
A. Short antennas are more likely to cause distortion of transmitted signals
B. Q of the antenna will be very low
C. Operating bandwidth may be very limited
D. Harmonic radiation may increase
C. Operating bandwidth may be very limited
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
Which of the following may cause receive interference to an HF transceiver installed in a vehicle?
A. The battery charging system
B. The fuel delivery system
C. The control computers
D. All these choices are correct
D. All these choices are correct
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.
In what configuration are the individual cells in a solar panel connected together?
A. Series-parallel
B. Shunt
C. Bypass
D. Full-wave bridge
A. Series-parallel
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.
What is the approximate open-circuit voltage from a fully illuminated silicon photovoltaic cell?
A. 0.02 VDC
B. 0.5 VDC
C. 0.2 VDC
D. 1.38 VDC
B. 0.5 VDC
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.
Why should a series diode be connected between a solar panel and a storage battery that is being charged by the panel?
A. To prevent overload by regulating the charging voltage
B. To prevent discharge of the battery through the panel during times of low or no illumination
C. To limit the current flowing from the panel to a safe value
D. To prevent damage to the battery due to excessive voltage at high illumination levels
B. To prevent discharge of the battery through the panel during times of low or no illumination
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.
What precaution should be taken when connecting a solar panel to a lithium iron phosphate battery?
A. Ground the solar panel outer metal framework
B. Ensure the battery is placed terminals-up
C. A series resistor must be in place
D. The solar panel must have a charge controller
D. The solar panel must have a charge controller
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.
