Radio Receivers
The controlled oscillator synthesizer is sometimes preferred over the direct one because

It is relatively free of spurious frequency
It is a simpler piece of equipment
It does not require crystal oscillator
Its frequency stability is better

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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 permit easier tracking
To allow adequate frequency coverage without switching
To help the image frequency rejection

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

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

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Radio Receivers
In a ratio detector

the output is twice that obtainable from a similar phase discriminator
the linearity is worse than in phase discriminator
the circuit is the same as in a discriminator, except that the diodes are reversed
stabilization against signal strength variations is provided

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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

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

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