Figure 2-22.30 MHz oscillator circuit, simplied schematic diagram.

TM 11-6625-467-34

Figure 2-22.30 MHz oscillator circuit, simplied schematic diagram.

represents 100-percent distortion. After this cali-

emitter has zero phase shift, thus sustaining circuit

oscillation. HIGH FREQ AMPL control R2 varies

bration is made, the high pass filter output (dis-

the dc level at the emitter of Q1. This voltage con-

tortion detector output) is connected to the meter

trols the oscillator output level. Transistor Q2 is the

circuit. The high pass filter removes the 1-kHz fun-

output emitter follower circuit. The circuit trans-

damental frequency and leaves only the harmonic

forms the high oscillator output impedance to a low-

components of the signal present at the distortion

output impedance. The emitter follower circuit also

output. The meter indicates the voltage value of the

harmonic components present at the distortion out-

prevents the external circuits from loading the

crystal oscillator.

put, thereby giving an indication of the harmonic

distortion of the input signal.

2-28. Distortion Detector

2-29. Audio Amplifier/Detector

(fig. 2-23)

(fig. 2-24)

The distortion detector measures the harmonic dis-

The audio amplifier/detector circuit in conjunction

tortion of a 1 kHz signal. The circuit is composed of

with the TEST METER performs as an electronic

transistor amplifier Q6, 2-kHz high pass filter FL1,

voltmeter in the test set. The CIRCUIT SELECTOR

and associated components. The distorted 1-kHz sig-

switches connect various oscillator and module cir-

nal is applied to the distortion detector input. DIST

DET control R4 adjusts the signal input level.

cuit outputs in the frequency range of 150-Hz to

500-kHz to the audio amplifier/detector input. The

Capacitor C19 couples the input signal from R4 to

circuit amplifies and rectifies signals and applies the

the base of transistor Q6. The amplifier circuit of

resulting dc voltage to the meter circuit. Capacitor

transistor Q6 amplifies the signal and applies it to

filter FL1 and to a voltage divider consisting of R35

C15 couples the input signal to the base of transistor

Q1. The emitter follower circuit of Q1, current ampli-

and R36. Both the voltage divider output and the

fies the signal and applies it to the base of Q2

high pass filter output connect to the meter circuit

through coupling capacitor C16. The amplifier cir-

through switches. In the use of the distortion detec-

cuit of transistor Q2 amplifies the signal and applies

tor, first the meter circuit is switched to the voltage

it to the base of transistor Q3 through C19 and sen-

divider output and DIST DET control R4 is adjusted

for a predetermined meter reading. This reading

sitivity control R11. Resistor R11 controls the signal

2-63