LOCAL OSCILLATOR MODULE A1500.

TM 11-5820-670-30

1-15. MIXER AND BUFFER AMPLIFIER A1400 (RECEIVE MODE). (CONT)

Mixer V1401 is the last of three vacuum tubes in the receiver section. During the receive operation it

accepts the following inputs:

Amplified frequency-modulated rf from module A1300

A frequency from the local oscillator which is, in the

band, 11.5 MHz above or in

band

11.5 MHz below the frequency of module A1300.

The two signals applied to the mixer are heterodyned (mixed) to produce an if. which carries audio

intelligence. The 11.5 MHz if. output from the mixer is applied to the following:

If. Attenuator Module A4900

Buffer Amp Q1401

Buffer amp Q1401 does not operate in the receive mode; therefore, no signal is present at its output.

In the receive mode, transistor Q1401 cannot conduct because there is no dc voltage to bias it. In the

transmit mode of operation only, 16 vdc biases buffer amp Q1401.

For a discussion of the mixer and buffer amplifier operating in transmit mode, see paragraph 1-43.

1-26. LOCAL OSCILLATOR MODULE A1500.

EL1AT102

1-24