Figure 2-1. Frequency selector switch circuit, functional diagram.

TM 11-6625-467-34

Figure 2-1. Frequency selector switch circuit, functional diagram.

LECTOR B or C connects the RF amplifier/detector

sired voltage. C I R C U I T SELECTOR A selects

output to CIRCUIT SELECTOR A. CIRCUIT SE-

either CIRCUIT SELECTOR B or C and connects

LECTOR A connects either CIRCUIT SELECTOR

the selected output to the audio amplifier/detector

B or C to the PRESS TO TEST switch. The PRESS

input. The audio amplifier/detector amplifies and

TO TEST switch connects the dc voltage to the

detects the ac input voltage and produces a dc out-

TEST METER for readout.

put voltage that is proportional to the input ampli-

c. Dc Voltage Measurements. Dc voltages in the

tude. CIRCUIT SELECTOR A also connects the

test set are measured as shown in C, figure 2-2.

audio amplifier/detector output to the PRESS TO

The dc voltages connect to CIRCUIT SELECTOR C.

TEST switch. The PRESS TO TEST switch con-

CIRCUIT SELECTOR C selects the dc voltage to be

n e c t s the dc voltage to the TEST METER to

m e a s u r e d and applies the voltage to the TEST

readout.

METER through the PRESS TO TEST switch.

b. RF Voltage Measurement. Radio frequency

(RF) voltages in the test set, within the frequency

2-5. 150 Hz Oscillator/Counter Signal Paths

range of 3 to 70 megahertz, are measured as shown

in B, figure 2-2. The RF voltages are connected to

The 150 Hz oscillator/counter is a single circuit that

front panel connectors RF VM1, RF VM2, RF VM3,

performs two functions as follows:

and RF VM4 by RF jumper cables supplied with the

a. 150 Hz Oscillator. The circuit is connected as

equipment. The four inputs, RF VM1 through RF

an oscillator by CIRCUIT SELECTOR D (position 1)

VM4, match 50 ohm, 150 ohm, 200 ohm, and 600 ohm

which connects the output of the 150 Hz amplifier to

input impedances, respectively. The RF amplifier/

the circuit input. The 150 CPS AMPL control varies

detector amplifies and detects the RF input voltage

the oscillator output level. CIRCUIT SELECTOR B

and produces a dc output voltage that is propor-

(position 4) connects the 150 Hz oscillator to the

tional to the RF input amplitude. CIRCUIT SE-

2-3