Honeywell Bendix/King KX 165A Maintenance Manual page 42

BENDIX/KING
4.3.4.6 Mixer
Q7 is an N-channel depletion type dual gate MOS-FET that is the active component in the Mixer.
The output from the synthesizer's VCO buffer amplifier is incident upon one of the gates and
serves as the LO (Local Oscillator) for the Mixer. The GS signal is incident upon the other gate,
and is the RF input to the Mixer. The LO is 30 kHz below the GS signal so that a 30 kHz IF (in-
termediate Frequency) is generated. Conversion loss from the input RF lever to the IF power level
absorbed by the IF Amplifier #1 is 13 dB. This loss is due mainly to an impedance mismatch be-
tween the Mixer and the IF Amplifier #1 causing most of the Mixer's output power to be dissipated
in R2.
4.3.4.7 IF Amplifier #1
Q5 is the active device in the IF Amplifier #2. Gain at the 30 kHz IF is 30 dB.
4.3.4.8 50 kHz Low Pass Filter
This 9 pole filter has a Chebyshev response and a -6dB pass band of 50 kHz minimum. Out of
band rejection is typically 60 dB at 90 kHz. Ultimate refection is greater than 70 dB.
4.3.4.9 IF Amplifier #2
Q1 is the active device in the IF Amplifier #2. Gain at the 30 kHz IF is 30 dB. This is the power
gain from the power absorbed by the Amplifier #2 input to the power delivered to R10.
4.3.4.10 IF Amplifier #3
U4 is an IF VGA (Variable Gain Amplifier). Its gain is adjusted by the IF AGC amplifier. The RF
VGA has more effect on receiver gain over the power range of -90 dBm to -50 dBm than the IF
VGA. From -105 to -90 dBm and -50 to -33 dBm the IF VGA has more effect on overall receiver
gain than the RF VGA.
4.3.4.11 IF Amplifier #4
Q2 is the active device in the IF Amplifier #4. Gain at the 30 kHz IF is 25 dB. This is the power
gain from the power absorbed by the Amplifier #4 input to the power delivered to the Detector.
Rev 0, Jun/2000 15610M00.RCD
KX 165A
Page 4-39