Hunt Generator

TM 11-5820-670-30

1-34. MASTER OSCILLATOR FREQUENCY CONTROL LOOP. (CONT)

The hunt cutoff detector is basically a diode clipper and a filter, which clips off the negative half of the

rf sine wave, filters it, and outputs a constant positive dc level. This dc level is applied to the hunt

generator where it biases off the sawtooth generator. Consequently, no sawtooth voltage is applied to

the master oscillator.

When the master oscillator drifts off frequency, the mixer's difference frequency moves further away

from 11.5 MHz. Consequently, the if. filters attenuate the signal, causing reduced amplification by

the receiver if. amplifiers. If the master oscillator is far enough off frequency ( 400 kHz or more),

the positive half of the rf sine wave clipped by the hunt cutoff detector is very low in amplitude, resulting

in a reduced dc level applied to hunt generator (9).

The reduced dc signal is not strong enough to bias the sawtooth generator off, so it begins to output a

sawtooth voltage.

Hunt Generator

The sawtooth generator in the hunt detector applies a sawtooth voltage to the master oscillator when its

frequency varies from the mechanically selected frequency by more than 400 kHz. The sawtooth

voltage brings the master oscillator close enough to the correct frequency for the phase discriminator

to fine tune it.

Output from the hunt generator occurs primarily when the tuning dials are switched to another fre-

quency. Once the phase discriminator takes over master oscillator frequency control, the sawtooth

generator is once again biased off.

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