CRS BALANCED MIXER A3200. - TM-11-5820-401-34-30019

TM 11-5820-401-34-3/0967-LP-432-3060

LOCAL OSCILLATOR AFC/CRYSTAL REFERENCE SYSTEM. (CONT)

1-15.

The hunt discriminator can coarse tune the local oscillator when its frequency error is within

400 kHz.

FINE TUNING THE LOCAL OSCILLATOR

The hunt discriminator is sensitive to large errors in local oscillator frequency, while the phase dis-

criminator (14) responds to small errors. The phase discriminator compares the fixed output of the

reference oscillator (15) with the variable output of the limiter (10). When the two input signals are of

unequal frequency (due to incorrect local oscillator frequency), the phase difference causes the

phase discriminator to output a dc error voltage which is applied to the local oscillator to bias it into

correct frequency operation.

1-16.

CRS BALANCED MIXER A3200.

12 HARMONICS

FROM A3100

HARMONIC

GENERATOR

41.50 TO 64.45

MHz FROM

LOCAL OSCILLATOR

The balanced mixer accepts inputs from the following two sources:

1. The local oscillator through the high-pass Filter FL3002.

2. The harmonic generator.

Local oscillator signals are applied to the mixer through a buffer amplifier to prevent loading down the

local oscillator. Twelve frequencies, 1 to 12 MHz, are applied to the mixer along with the local

oscillator's output. The signals are heterodyned to produce four strong mixed output frequencies.

BALANCED MIXER OPERATING EXAMPLE

Assume that the radio is tuned to 30 MHz, in which case the local oscillator runs at 41.50 MHz. The

41.50-MHz frequency is mixed with 12 signals generated by the harmonic generator, producing mixed

output containing each of the 12 harmonics, the local oscillator frequency, and sum and difference

frequencies listed below.

1-9