HOMING SIGNAL FLOW.

TM 11-5820-670-30

1-50. HOMING SIGNAL FLOW.

Homing operation is available on any of 920 channels in the frequency range of 30.00 to 75.95 MHz.

The homing circuit provides information to the aircraft homing indicator concerning the aircraft

heading with respect to a transmitting station. To follow the homing circuits signal path, see FO-7

while reading the text in this paragraph.

When the control unit mode selector switch is set to HOME, + 27.5 vdc is connected through the

control unit causing relay K4502 in rf control assembly A4500 to energize. Relay K4502 in turn applies

+ 16 vdc to energize the homing circuits.

Input signals from left and right homing antennas (1) are applied through diode switch (2) to rf

attenuator (3). 100 Hz oscillator (4) alternately injects the two signals from the antennas into the rf

attenuator circuit at a 100 Hz rate. The rf attenuator, controlled by a voltage from homer rf agc

amplifier (14), attenuates strong received signals that may damage the receiver circuitry. Output

signals from the rf attenuator are applied through homing relay K4502 to antenna tuning and protection

circuits (5).

Gearbox assembly A9700 (6) tunes the circuits for the received signal which are applied to first rf amp

(7) for amplification. Amplified rf is amplified further in second rf amplifier (8) and then applied to

mixer (9) to be heterodyned with the frequency of local oscillator (10).

The 11.5 MHz if. output of mixer A1400 is applied to if. attenuator (11) which reduces the signal

level in the homing mode. The if. attenuation prevents overloading under the strongest operating

conditions. The output of the if. attenuator is coupled through band-pass filter FL4001 (12) and the

signal is processed through the remaining portion of the receiver as indicated in paragraph 1-13,

except that the am components of the if. signal (if.-am signal) is detected in the fourth if. amp by the

hunt cutoff detector p/o module A4200 (13).

The if. am signal from the hunt cutoff detector is applied to rf agc amp (14), if. agc amp (15), and

off-course signal amp (16). The homer rf agc amplifier supplies agc voltage to rf attenuator circuit

(3) which controls the gain of the received signal. Homer if. agc amp (15) supplies agc voltage to if.

attenuator (11) which controls the gain of the 11.5 MHz if. signal.

Off-course signal amplifier (16) amplifies the if.-am signal and applies it to synchronous detector

(17). The synchronous detector compares the if.-am signal with the 100 Hz square wave produced by

100 Hz oscillator (4) and applies a dc signal to the homing indicator vertical needle.

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