MB MODULATION AND VOR/LOC 1020 HZ SIGNAL

TM 11-6625-2976-40

1-16. MODULATING CIRCUITS. (CONT)

Delete Switch Open Mode

Pressing front panel 30 VAR DELETE switch S19 or 30 REF DELETE switch S20 opens (removes) the

30 Hz variable or the 30 Hz reference signal from the VOR composite signal.

MB MODULATION AND VOR/LOC 1020 HZ SIGNAL

Refer to (FO-6) while reading the text in this section.

Operating voltage is applied to the MB modulating circuits in the circuit card assembly and MB rf

module Al through front panel PWR switches S6 and S2. MB PWR switch S6 also determines whether

the 1020 Hz signal is available to LOC/VOR modulating circuits or 400, 1300, and 3000 Hz are avail-

able for MB modulation.

MB PWR Switch OFF

When MB PWR switch S6 is in the OFF position, operating voltage is applied to the 1020 Hz generating

circuits in the MB vco. The MB vco 1020 Hz output is then available for use in the VOR or LOC mode.

Operating voltage is applied to the selected segment (VOR or LOC) of the VOR/LOC/M B select switch

In the circuit card assembly by setting the front panel VOR or LOC 1020 Hz switch to the ON (closed)

position.

The closed VOR 1020 Hz switch allows the VOR/LOR/MB select switch to complete the 1020 Hz path to

the VOR modulating circuits. Likewise, the closed LOC 1020 Hz switch allows the VOR/LOC/MB select

switch to complete the 1020 Hz path to LOC modulating circuits.

MB PWR Switch ON

Placing MB PWR switch S6 In the ON position inhibits the ability of the MB vco to generate 1020 Hz and

enables the blue, yellow, and white MB front panel switches. By pressing one of the MB front panel

switches, operating voltage is applied to MB vco in the following manner:

1. When blue MB switch S3 is depressed, operating voltage is applied to the 400 Hz generating

segment of the MB vco.

2. When yellow MB switch S4 is depressed, operating voltage is applied to the 1300 Hz generating

segment of the MB vco.

3. When white MB switch S5 Is depressed, operating voltage is applied to the 3000 Hz generating

segment of the MB vco.

The VOR/LOC/MB select switch applies the selected signal through the MB MODULATION AMP to MB

rf module A1.

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