2-16. RECEIVE HOMING SIGNAL PATH
Figure 2-5 shows the homing circuits, The AGC and SIG STR RCV inputs are from the lF/demodulator module in
the rf receive signal path (paragraph 2-8). The AGC input is a 150 Hz square wave that has an amplitude propor-
tional to the amplitude difference between the left and right homing antennas. This signal is applied to sample
and hold circuits which change it to a dc voltage proportional to the rf level at the right and left homing antennas.
The dc voltages are applied to inverting and non-inverting buffers and summed to produce a difference voltage.
This voltage (STEERING RIGHT) drives the homing indicator meter.
The SIG STR RCV input is a dc voltage proportional to the received rf signal strength. This input is processed to
develop the SIG STR RTN, STA APPROACH, and NOISE PRESENT outputs. The SIG STR RTN signal activates a flag
in the homing indicator when the SIG STR RCV input exceeds a reference corresponding to -103 dBm. The STA
APPROACH output drives the station approach meter in the homing indicator. The NOISE PRESENT output is a
logic 1 or logic O developed by comparing SIG STR RCV to a reference. The NOISE PRESENT output is used by the
Figure 2-5. Homing Circuits Block Diagram