Station Assembly, Practice and Safety
frequency and phase modulation fundamentals
What may happen if an FM transmitter is operated with the microphone gain or deviation control set too high?
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It may cause digital interference to computer equipment
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It may cause atmospheric interference in the air around the antenna
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It may cause interference to other stations operating on a higher frequency band
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Correct AnswerIt may cause interference to other stations operating near its frequency
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What may your FM hand-held or mobile transceiver do if you shout into its microphone?
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Correct AnswerIt may cause interference to other stations operating near its frequency
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It may cause digital interference to computer equipment
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It may cause atmospheric interference in the air around the antenna
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It may cause interference to other stations operating on a higher frequency band
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What can you do if you are told your FM hand-held or mobile transceiver is overdeviating?
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Talk louder into the microphone
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Let the transceiver cool off
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Change to a higher power level
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Correct AnswerTalk farther away from the microphone
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What kind of emission would your FM transmitter produce if its microphone failed to work?
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A frequency-modulated carrier
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An amplitude-modulated carrier
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Correct AnswerAn unmodulated carrier
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A phase-modulated carrier
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Why is FM voice best for local VHF/UHF radio communications?
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Correct AnswerIt has high-fidelity audio which can be understood even when the signal is somewhat weak
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The carrier is not detectable
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It is more resistant to distortion caused by reflected signals
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Its RF carrier stays on frequency better than the AM modes
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What is the usual bandwidth of a frequency-modulated amateur signal?
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Correct AnswerBetween 10 and 20 kHz
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Less than 5 kHz
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Between 5 and 10 kHz
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Greater than 20 kHz
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What is the result of overdeviation in an FM transmitter?
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Correct AnswerOut-of-channel emissions
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Increased transmitter power
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Increased transmitter range
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Poor carrier suppression
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What emission is produced by a reactance modulator connected to an RF power amplifier?
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Multiplex modulation
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Amplitude modulation
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Pulse modulation
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Correct AnswerPhase modulation
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Why isn't frequency modulated (FM) phone used below 29.5 MHz?
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The transmitter efficiency for this mode is low
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Harmonics could not be attenuated to practical levels
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The frequency stability would not be adequate
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Correct AnswerThe bandwidth would exceed limits in the Regulations
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You are transmitting FM on the 2 metre band. Several stations advise you that your transmission is distorted. A quick check with a frequency counter tells you that the transmitter is on the proper frequency. Which of the following is the most probable cause of the distortion?
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Correct AnswerThe frequency deviation of your transmitter is set too high
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The power supply output voltage is low
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The repeater is reversing your sidebands
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The frequency counter is giving an incorrect reading and you are indeed off frequency
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FM receivers perform in an unusual manner when two or more stations are present. The loudest signal, even though it is only two or three times as loud as the other signals, will be the only transmission demodulated. This is called:
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attach effect
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interference effect
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surrender effect
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Correct Answercapture effect
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