IF. ATTENUATOR MODULE A4900 (RECEIVE MODE).

TM 11-5820-670-30

1-27. IF. ATTENUATOR MODULE A4900 (RECEIVE MODE).

EL1AT103

In receive mode, if. attenuator module A4900 allows if. signals from the mixer to pass through the

diode circuitry with minimum attenuation.

Constant 16 vdc from homer relay K4502 is applied to a zener diode in the if. attenuator module. This

causes the zener diode to apply an increased level of voltage to the diode circuitry, fully biasing the

diodes. When the diodes in the diode circuitry are fully biased, a direct unattenuated path is available

for the if. from the mixer to flow to first and second if. amplifier module A4100.

The if. attenuator functions in transmit mode exactly as it does in receive mode. For a discussion of

the if. attenuator operation in homing mode, see paragraph 1-52.

1-28. FIRST AND SECOND IF AMPLIFIER A4100.

The 11.5 MHz if. carrying audio intelligence from the if. attenuator is applied through band-pass filter

FL4001 to Q4101, which performs the first stage of amplification. Second if. amp Q4102 provides a

second stage of amplification.

Amplified 11.5 MHz if. from the second if. amplifier is applied through filter FL4002 to module A4200.

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