SYNCHRONOUS DETECTOR-continued

TM 11-5820-670-30

1-53. HOMER-DETECTOR AMPLIFIER ASSEMBLY A4800. (CONT)

The output if.-am signal from amplifier Q4810 is applied to transistors Q4803 and Q4804 which form

the synchronous detector. The synchronous detector circuit is also driven by the 100 Hz oscillator

used to alternately switch the homing signals from the left and right antennas into the circuit.

When the positive and negative half cycles of the homer if.-am signal have equal strength, the outputs

of Q4803 and Q4804 are equal in amplitude and opposite in phase which causes the homing indicator

vertical needle to be centered.

When there is unequal signal strength between the positive and negative half cycles, the vertical

needle indicates an average output between the two signals.

The homing indicator vertical needle allows the pilot to determine if the aircraft is off course left or off

course right. When the vertical needle is centered, the aircraft is perfectly alined with the transmitting

station.

EL1AT133

The signal strength amplifier controls the deflection of the homing indicator horizontal needle. With no

signal input, if. agc voltage is maximum and transistor Q4811 conducts, causing the horizontal

indicator deflection to be maximum.

As the level of the received signal increases, if. agc voltage decreases, which reduces conduction of

Q4811 and causes less deflection of the horizontal needle. Minimum deflection of the indicator

(needle centered) occurs at maximum received signal level.

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