Radio Receivers
In a ratio detector

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

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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
In a broadcast superheterodyne receiver, the

Mixer input must be tuned to the signal frequency
RF amplifier normally works at 455 kHz above the carrier frequency
Local oscillator frequency is normally double the IF
Local oscillator operates below the signal frequency

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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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