Transmitter - Honeywell Bendix/King KX 165A Maintenance Manual

BENDIX/KING KX 165A
4.2.2

TRANSMITTER

The transmitter produces an amplitude modulated (AM) signal within the COM BAND frequency
range of 118 to 137 MHz. The output power of the signal at the COM ANT is 10 watts minimum.
Refer to figure 4-3 for the following description of the transmitter.
The audio from the microphone is amplified and passed through a mic gain control which estab-
lishes the audio level used to modulate the transmitter. The mic audio signal is limited before it
passes through the response amplifier which drives the modulator/power control stage that ampli-
tude modulates the transmitter.
A buffered RF signal derived from the frequency synthesizer drives the transmitter chain. The
chain consists of the predriver, driver, final amplifier, LPF and Directional Coupler. The directional
coupler is used to sample the RF power. The sampled RF power is detected and buffered, then
routed to the modulator/power control stage to maintain the transmitter power output. The output
of the modulator/power control stage modulates the gate of the final amplifier and also drives a
low level modulator which modulates the predriver.
The T/R switch is embedded within the LPF. In transmit, the receiver is isolated by a PIN diode.
In receive, the PIN diode conducts the received signal to the RECEIVER BOARD.
Rev 0, Jun/2000 15610M00.RCD Page 4-9