Radio Receivers
The frequency generated by each decade in a direct frequency synthesizer is much higher than the frequency shown; this is done to

Reduce the number of decades
Reduce the spurious frequency problem
Increase the frequency stability of the synthesizer
Reduce the number of crystals required

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Radio Receivers
Indicate the false statement in connection with communications receivers.

Double conversion is used to improve image rejection
A product demodulator could be used for the reception of Morse code.
Variable sensitivity is used to eliminate selective fading
The noise limiter cuts off the receiver’s output during a noise pulse.

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Radio Receivers
The local oscillator of a broadcast receiver is tuned to a frequency higher than the incoming frequency

Because otherwise an intermediate frequency could not be produced
To allow adequate frequency coverage without switching
To permit easier tracking
To help the image frequency rejection

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Radio Receivers
If a FET is used as the first AF amplifier in a transistor receiver, this will have the effect of

Reducing the effect of noise at low modulation depths
Improving the selectivity of the receiver
Reducing the effect of negative-peak clipping
Improving the effectiveness of the AGC

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