Figure 2-9. 30 MHz oscillator circuit, functional diagram.

TM 11-6625-467-34

Figure 2-9. 30 MHz oscillator circuit, functional diagram.

CIRCUIT SELECTOR C (position 1). The DIST

to the ac voltmeter circuit.

DET control is adjusted for a specified reading on

2-18. RF Power Detector Signal Paths

t h e TEST METER. This reading represents 100

(fig. 2-16)

percent distortion. Next, CIRCUIT SELECTOR C

The test set RF power detector circuit provides a

is switched to position O. The amplifier output must

means to measure the AN/ARC-54 power amplifier

n o w pass through highpass filter FL1 before it

output power. The power amplifier connects to J9

reaches the voltmeter circuit. The highpass filter

only passes frequencies above 1 kHz; therefore,

o n the test set when the AN/ARC-54 RF sub-

the fundamental frequency is filtered out and all

chassis is plugged into J2. Connector J9 applies the

RF power to attenuator AT1 which provides a 50

that remain are the harmonic components gener-

ated as a result of nonlinear amplification in the

ohm load impedance for the power amplifier. The

attenuator also acts as a power divider and applies

module circuit under test. The TEST METER indi-

a portion of the input power to power detector A14.

cates the amplitude of these harmonic components

The power detector rectifies the RF signal and pro-

as a percentage of the original signal amplitude.

duces a dc output voltage that is proportional to the

2-17. 500 kHz Discriminator Signal Paths

RF input voltage. The dc output of the power de-

(fig. 2-15)

tector is applied to CIRCUIT SELECTOR B. CIR-

The 500 kHz discriminator demodulates the fm 500

CUIT SELECTOR B (position 0) connects the dc

kilohertz output of the transmit audio module. In

voltage to CIRCUIT SELECTOR A. When CIR-

position 3, CIRCUIT SELECTOR A connects the

CUIT SELECTOR A is in position O, it transfers the

dc voltage to the dc voltmeter circuit for readout.

transmit audio module 500 kilohertz output to the

discriminator input. The discriminator output con-

2-19. Signal Paths (Operating Procedures)

nects to one of two places through CIRCUIT SE-

of CIRCUIT SELECTOR Switches

LECTOR switches. In position 2, CIRCUIT SE-

The test set contains a group of functional circuits

LECTOR B connects the discriminator output to the

such as oscillators, amplifiers, and detectors, con-

distortion detector circuit. CIRCUIT SELECTOR

n e c t e d together by a switching arrangement for

C, in position 2, connects the discriminator output

2-10