A-005-06: FM transmitter, repeater circuits
A-005-06-01:
If the signals of two repeater transmitters mix together in one or both of their final amplifiers and unwanted signals at the sum and difference frequencies of the original signals are generated, what is this called?
Intermodulation interference
Neutralization
Adjacent channel interference
Amplifier desensitization
A-005-06-02:
How does intermodulation interference between two repeater transmitters usually occur?
When they are in close proximity and the signals mix in one or both of their final amplifiers
When the signals are reflected in phase by aircraft passing overhead
When they are in close proximity and the signals cause feedback in one or both of their final amplifiers
When the signals are reflected out of phase by aircraft passing overhead
A-005-06-03:
How can intermodulation interference between two repeater transmitters in close proximity often be reduced or eliminated?
By installing a terminated circulator or ferrite isolator in the feed line to the transmitter and duplexer
By installing a low-pass filter in the antenna feed line
By installing a high-pass filter in the antenna feed line
By using a Class C final amplifier with high driving power
A-005-06-04:
If a receiver tuned to 146.70 MHz receives an intermodulation product signal whenever a nearby transmitter transmits on 146.52, what are the two most likely frequencies for the other interfering signal?
146.34 MHz and 146.61 MHz
146.88 MHz and 146.34 MHz
146.01 MHz and 147.30 MHz
73.35 MHz and 239.40 MHz
A-005-06-05:
What type of circuit varies the tuning of an amplifier tank circuit to produce FM signals?
A phase modulator
A balanced modulator
A double balanced mixer
An audio modulator
A-005-06-06:
What audio shaping network is added at an FM transmitter to attenuate the lower audio frequencies?
A pre-emphasis network
An audio prescaler
A heterodyne suppressor
A de-emphasis network
A-005-06-07:
Which type of filter would be best to use in a 2-metre repeater duplexer?
A cavity filter
A DSP filter
An L-C filter
A crystal filter
A-005-06-08:
The characteristic difference between a phase modulator and a frequency modulator is:
pre-emphasis
the centre frequency
de-emphasis
frequency inversion
A-005-06-09:
In most modern FM transmitters, to produce a better sound, a compressor and a clipper are placed:
between the audio amplifier and the modulator
between the multiplier and the PA
between the modulator and the oscillator
in the microphone circuit, before the audio amplifier
A-005-06-10:
Three important parameters to be verified in an FM transmitter are:
linearity, frequency deviation and frequency stability
distortion, bandwidth and sideband power
modulation, pre-emphasis and carrier suppression
frequency stability, de-emphasis and linearity
A-005-06-11:
For a repeater to operate automatically, the circuit that determines when to turn the transmitter on and off is the:
carrier operated relay
limiter
automatic identifier
multiplier
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