RF CONTROL ASSEMBLY P/O MODULE A4500 (RECEIVE MODE).

TM 11-5820-670-30

1-21. RF CONTROL ASSEMBLY P/O MODULE A4500 (RECEIVE MODE).

EL1AT097

Frequency modulated rf from the communications antenna is applied through the primary of trans-

former T4501 to the sidetone gate detector. Very low levels of rf are coupled-to the secondary of

transformer T4501 and then applied to the diode circuits. The diode circuits will not produce-an output

unless the rf level is 0.6 watt or greater. In receive mode, the rf level entering the diode circuits is well

below 0.6 watt; therefore, the reflectometer will not operate.

Low level rf entering the sidetone gate detector from the primary of transformer T4501 is applied to

both transmit/receive relay K4501 and transistor Q4501. In receive mode, rf modulated signals

entering relay K4501 are applied to homing relay K4502 and then to antenna tuning and protection

circuits module A1100.

Rf signals applied to transistors Q4501 and Q4502 must be 0.6 watt or greater to bias the transistors.

In receive mode, the rf signal is well below 0.6 watt, therefore, both Q4501 and Q4502 are not biased.

When Q4501 and Q4502 are not biased, the sidetone gate detector will not operate and no sidetone

gate signal is generated.

The reflectometer and sidetone gate detector will operate in transmit mode and are discussed in

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