Switches in Normal Mode

TM 11-6625-2976-40

1-16. MODULATING CIRCUITS.(CONT)

VOR MODULATION (CONT)

Both delete switches are normally closed. In its normal or unlit position, the VAR 10 switch

provides the paths through the circuit card assembly variable/reference delete and NORMAL/VAR

select switches for the reference and front panel bearing select switch-selected 30 Hz signals.

Switches in Normal Mode

With the front panel VOR 30 REF, 30 VAR, switches in their normal positions, the 30 Hz reference

signal is applied through a 30 Hz reference and band pass filter and phase shift network to the loop

summing amp. Meanwhile, the switch-selected (bearing) 30 Hz signal is applied through another 30

Hz band pass filter, the normal portion of the 30 Hz normal/variable select and a 30 Hz variable phase

shift network. The output of the phase shift network and a developed 9960 Hz signal from the 9960 Hz

vco are applied to the VOR composite amp for distribution to VOR rf module A5. The VOR composite

amp also will apply the 1020 Hz signal generated by the MB vco to VOR rf module A5 when 1020 Hz

switch S22 is closed.

The 9960 Hz signal applied to the VOR composite amp is generated by a 9960 Hz vco. The 30 Hz signal

from the loop summing amp frequency modulates the 9960 Hz signal.

The 9960 Hz vco is kept on frequency by a phase locked loop correction network, which uses the 60 Hz

fundamental frequency generated by the 3.932 MHz crystal oscillator and frequency divider as a phase

reference for the vco output. That is, the correction network keeps the vco output in phase with the 60

Hz reference signal. The output of the phase locked loop correction network is applied to the 9960 Hz

vco through the loop summing amp.

VAR 10 LAMP/SWITCH VARIABLE MODE

Pressing the VAR 10 lamp/switch enables the VOR variable mode of operaticn. In the variable

mode, the front panel bearing select switch-selected 30 Hz signal is applied through variable control

R3 (FO-3) to the 30 Hz VARIABLE PHASE SHIFT NETWORK. Variable control R3 is used to vary the

phase of the select signal 10 in bearing.

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