Topic G8: Signals and Emissions
G8A-2011: Carriers and modulation: AM; FM; single and double sideband; modulation envelope; overmodulation
What is the name of the process that changes the envelope of an RF wave to carry information?
Spread spectrum modulation
What is the name of the process that changes the phase angle of an RF wave to convey information?
What is the name of the process which changes the frequency of an RF wave to convey information?
What emission is produced by a reactance modulator connected to an RF power amplifier?
What type of modulation varies the instantaneous power level of the RF signal?
Frequency shift keying
Pulse position modulation
What is one advantage of carrier suppression in a single-sideband phone transmission?
The available transmitter power can be used more effectively
Audio fidelity is improved
Greater modulation percentage is obtainable with lower distortion
Simpler receiving equipment can be used
Which of the following phone emissions uses the narrowest frequency bandwidth?
Which of the following is an effect of over-modulation?
What control is typically adjusted for proper ALC setting on an amateur single sideband transceiver?
Transmit audio or microphone gain
The RF clipping level
Antenna inductance or capacitance
What is meant by flat-topping of a single-sideband phone transmission?
Signal distortion caused by excessive drive
Signal distortion caused by insufficient collector current
The transmitter's automatic level control is properly adjusted
The transmitter's carrier is properly suppressed
What happens to the RF carrier signal when a modulating audio signal is applied to an FM transmitter?
The carrier frequency changes proportionally to the instantaneous amplitude of the modulating signal
The carrier frequency changes proportionally to the amplitude and frequency of the modulating signal
The carrier amplitude changes proportionally to the instantaneous frequency of the modulating signal
The carrier phase changes proportionally to the instantaneous amplitude of the modulating signal
What signal(s) would be found at the output of a properly adjusted balanced modulator?
Both upper and lower sidebands
Either upper or lower sideband, but not both
Both upper and lower sidebands and the carrier
The modulating signal and the unmodulated carrier
G8B-2011: Frequency mixing; multiplication; HF data communications; bandwidths of various modes; deviation
What receiver stage combines a 14.250 MHz input signal with a 13.795 MHz oscillator signal to produce a 455 kHz intermediate frequency (IF) signal?
If a receiver mixes a 13.800 MHz VFO with a 14.255 MHz received signal to produce a 455 kHz intermediate frequency (IF) signal, what type of interference will a 13.345 MHz signal produce in the receiver?
What is another term for the mixing of two RF signals?
What is the name of the stage in a VHF FM transmitter that generates a harmonic of a lower frequency signal to reach the desired operating frequency?
Why isn't frequency modulated (FM) phone used below 29.5 MHz?
The wide bandwidth is prohibited by FCC rules
The transmitter efficiency for this mode is low
Harmonics could not be attenuated to practical levels
The frequency stability would not be adequate
What is the total bandwidth of an FM-phone transmission having a 5 kHz deviation and a 3 kHz modulating frequency?
What is the frequency deviation for a 12.21-MHz reactance-modulated oscillator in a 5-kHz deviation, 146.52-MHz FM-phone transmitter?
Why is it important to know the duty cycle of the data mode you are using when transmitting?
Some modes have high duty cycles which could exceed the transmitter's average power rating.
To aid in tuning your transmitter
To allow time for the other station to break in during a transmission
All of these choices are correct
Why is it good to match receiver bandwidth to the bandwidth of the operating mode?
It results in the best signal to noise ratio
It is required by FCC rules
It minimizes power consumption in the receiver
It improves impedance matching of the antenna
What does the number 31 represent in PSK31?
The approximate transmitted symbol rate
The version of the PSK protocol
The year in which PSK31 was invented
The number of characters that can be represented by PSK31
How does forward error correction allow the receiver to correct errors in received data packets?
By transmitting redundant information with the data
By controlling transmitter output power for optimum signal strength
By using the varicode character set
By using a parity bit with each character
What is the relationship between transmitted symbol rate and bandwidth?
Higher symbol rates require higher bandwidth
Symbol rate and bandwidth are not related
Lower symbol rates require higher bandwidth
Bandwidth is constant for data mode signals
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