G8B: Frequency mixing; multiplication; HF data communications; bandwidths of various modes
G8B01:
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?
Mixer
BFO
VFO
Multiplier
G8B02:
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?
Image response
Local oscillator
Mixer interference
Intermediate interference
G8B03:
What stage in a transmitter would change a 5.3 MHz input signal to 14.3 MHz?
A mixer
A beat frequency oscillator
A frequency multiplier
A linear translator
G8B04:
What is the name of the stage in a VHF FM transmitter that selects a harmonic of an HF signal to reach the desired operating frequency?
Multiplier
Mixer
Reactance modulator
Pre-emphasis network
G8B05:
Why isn't frequency modulated (FM) phone used below 29.5 MHz?
The bandwidth would exceed FCC limits
The transmitter efficiency for this mode is low
Harmonics could not be attenuated to practical levels
The frequency stability would not be adequate
G8B06:
What is the total bandwidth of an FM-phone transmission having a 5 kHz deviation and a 3 kHz modulating frequency?
16 kHz
3 kHz
5 kHz
8 kHz
G8B07:
What is the frequency deviation for a 12.21-MHz reactance-modulated oscillator in a 5-kHz deviation, 146.52-MHz FM-phone transmitter?
416.7 Hz
101.75 Hz
5 kHz
60 kHz
G8B08:
How is frequency shift related to keying speed in an FSK signal?
Greater keying speeds require greater frequency shifts
The frequency shift in hertz must be at least four times the keying speed in WPM
The frequency shift must not exceed 15 Hz per WPM of keying speed
Greater keying speeds require smaller frequency shifts
G8B09:
What do RTTY, Morse code, PSK31 and packet communications have in common?
They are digital modes
They require the same bandwidth
They use on/off keying
They use phase shift modulation
G8B10:
When transmitting a data mode signal, why is it important to know the duty cycle of the mode you are using?
To prevent damage to your transmitter's final output stage
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
G8B11:
What part of the 20 meter band is most commonly used for PSK31 operation?
Below the RTTY segment, near 14.070 MHz
At the bottom of the slow-scan TV segment, near 14.230 MHz
At the top of the SSB phone segment, near 14.325 MHz
In the middle of the CW segment, near 14.100 MHz
G8B12:
What is another term for the mixing of two RF signals?
Heterodyning
Synthesizing
Cancellation
Multiplying
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