Automatic Bearing Circuitry

Page Title: Automatic Bearing Circuitry
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MIL-N-81857(AS)

3.4.30.1. Automatic Bearing Circuitry - The automatic

bearing output shall be presented to the ID-663/U as combined

m a g n e t i c heading-bearing signal.. Magnetic heading data will be

available from the aircraft compass system. An output accuracy

degradation of 0.5 degree is permissible when the equipment is

loaded with an impedance equivalent to three (2) ID-663/U instru-

ments in parallel.

3 . 4 . 3 0 . 2 C o u r s e D e v i a t i o n C i r c u i t r y - The course de-

viation output shall be presented to the vertical needle of the

ID-387/ARN as a deviation from the manually selected course

to or from the beacon). The impedance into which it operates

shall be maintained at 333 ohms.

3 . 4 . 3 0 . 2 . 1 C o u r s e D e v i a t i o n S e n s i t i v i t y - Course de-

viation sensitivity shall adjustable so that deviations of from

2.5 to 15 will provide 450 microarmperes into a load impedance

of 333 ohlns.

3.4.30.2.2 T o - F r o m I n d i c a t o r - The receiver-trans-

mitter shall provide outputs suitable to operate the To-From

I n d i c a t o r in the ID-387/ARN.

3 . 4 . 3 0 . 3 F l a p A l a r m - T h e flag alarm of the ID-387/ARN

shall be actuated and the flag shall disappear when reliable signals

above minimum usable are received from the ground station.

Upon loss of signal, the flag shall reappear. The flag shall be

in view in the absence of either 15 cycle or 135 cycle signals,

despite the fact that the automatic bearing indicator may be

operating on the 15 cycle signal only. Flag operation is also

required when the percentage of modulation of the 15 cycle or

135 cycle signal is below the point where adequate phase stabi-

lity between the two signals can be maintained.

3 . 4 . 3 1 D i s t a n c e C i r c u i t r y - The distance measuring

circuitry shall determine automatically the distance in nautical

miles of the equipment from the transponder by measuring the

time delay between the transmitted interrogation pulses and the

r e p l y pulses.

3 . 4 . 3 1 . 1 D i s t a n c e F l a g A l a r m - The equipment shall be

capable of operating (3) indicator flag alarms to show either pre-

sence or absence of an adequate signal. The flag shall be in full

view during the memory period.

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