Figure 2-8. 5.925 MHz oscillator circuit, functional diagram

TM 11-6625-467-34

Figure 2-8. 5.925 MHz oscillator circuit, functional diagram

2-15. 500 KHz Filter Signal Paths

voltmeter circuit connects to the crystal filter out-

put, and the oscillator frequency is adjusted for a

peak reading.

The 500 kilohertz filter circuit consists of two types

2-16. Distortion Detector Signal Paths

of filters, a bandpass filter and a crystal filter. The

circuits are used to check and calibrate the fre-

quency of the 500 kilohertz oscillator in the transmit

The distortion detector circuit measures distortion

audio module. In position 3, CIRCUIT SELECTOR

generated by various AN/ARC-54 module circuits.

D connects the transmit audio module 500 kilohertz

The distortion detector operates by use of a 1 kHz

frequency; therefore, the 1 kHz oscillator circuit

oscillator to the filter input through the 500 KC

FILTER control. The KC FILTER control adjusts

(para 2-6) is used in conjunction with the distortion

d e t e c t o r . The 1 kHz oscillator connects to the

the input amplitude to the filter circuit which can be

directly monitored by the ac voltmeter circuit. The

module circuit input. The circuit outputs connect to

bandpass filter (mechanical filter) has a center fre-

the CIRCUIT SELECTOR B. CIRCUIT SELECTOR

quency of 500 kHz and a bandwidth of 700 Hz at the

B, in position 0, 1, 2, or 3, connects the desired cir-

- 6 decibel (half voltage) level. To determine

c u i t to the distortion detector input. DIST DET

whether the frequency is within the 700 Hz of 500

(distortion detector) control R4 couples the CIR-

kHz, set the input level to the filter circuit to a

CUIT SELECTOR B output to the distortion detec-

desired level; then switch the ac voltmeter circuit to

tor circuit and adjusts the amplitude of the signal to

the bandpass filter output, The crystal filter has a

a desired level. Two steps are involved in using the

much narrower bandpass than the bandpass filter

distortion detector. First, the amplifier output is

and is used to adjust the oscillator frequency. The ac

connected directly to the voltmeter circuit through

2-9