Frequency Response and Distorsion, Receive Mode

TM 11-5820-509-35

placing SIDETONE GATE ADJUST control to OFF.

NOTE

Move the audio oscillator and frequency counter to

If the VOX ON lamp fails to light,

RCVR AUDIO IN jacks (J8 and J14). Slowly increase

adjust R40 (and R27, in extreme

the level of the 1700 Hz tone until clipping is noted on

cases) until it lights.

the oscilloscope display.

(4) Return the KEY switch to OFF and place

(2) Measure the level at RCVR AUDIO OUT

the SIDETONE GATE ADJUST control to OFF.

jacks (J7 and J13), using the output meter. The reading

g. Harmonic Distortion and Frequency Response,

must not be less than 1 watt in 300 ohms (18 volts rms).

Transmit Mode.

(3) Measure the voltage at +AGC jack (J10)

(1) Move the audio oscillator and frequency

with the multimeter. The reading must not be less than

counter to MIKE AMPL IN jacks (J5 and J11) and adjust

+14.0 volts dc.

the oscillator output frequency to 1700 Hz.

(4) Measure the voltage at -AGC jack (J9)

(2) Place the PTT switch to ON and observe

with the multimeter.

The reading must be more

the waveform at MIKE AMPL OUT jacks (J6 and J12)

negative than -5.5 volts dc.

with the oscilloscope. Increase the level of the audio

e. Frequency Response and Distorsion, Receive

oscillator output until clipping occurs on the waveform.

Mode.

Reduce the output of the audio oscillator until the

(1) Connect the distortion analyzer to RCVR

clipping disappears.

AUDIO OUT jacks (J7 and J13) together with the output

(3) The voltage measured at MIKE AMPL IN

meter.

jacks (J5 and J11) must not exceed 0.015 volt rms.

(2) Set the audio oscillator output frequency

(4) Maintain the level measured in step (3),

to 300 Hz and adjust the level at RCVR AUDIO IN jacks

and record the frequency response and harmonic

(J8 and J14) to 0.1 volt rms.

distortion at 300, 1000, 1700 and 3000 Hz.

(3) Record the audio output (in dB) and the

(5) The frequency response shall not vary

harmonic distortion (in %) that are present at RCVR

more than 2.5 dB from the value recorded at 1700 Hz.

AUDIO OUT jacks (J7 and J13). Record the +AGC

(6) The harmonic distortion shall not exceed

voltage at J10 and the -AGC voltage at J9.

5 % at any frequency.

(4) Repeat steps (2) and (3) with the oscillator

h. Frequency Response at Nominal Output,

output frequency set to 1000 1700 and 3000 Hz.

Transmit Mode.

NOTE

(1) Connect the audio oscillator and

Be sure that the audio level at RCVR

frequency counter to MIKE AMPL IN jacks (J5 and J11)

AUDIO IN jacks (38 and J14) are

and adjust the output level to 0.1 volt rms at 1700 Hz.

maintained at 0.1 volt when the test

(2) Maintain this output level and measure

frequency is adjusted.

the frequency response at 300, 1000, 1700, and 3000

(5) The frequency response shall not vary

Hz.

more than 3 dB from She value recorded at 1700 Hz.

(3) The frequency response shall not vary

(6) The harmonic distortion shall not exceed

more than +2.0 dB from the value measured at 1700

8 % at any frequency.

Hz.

(7) The +AGC voltage shall not be less than

i. CW Oscillator Operation Test.

+7.0 volts dc at any frequency.

(1) Disconnect the audio oscillator from the

(8) The -AGC voltage must be more negative

test fixture.

Connect the oscilloscope, frequency

than -3.0 volts dc at any frequency.

counter, and loudspeaker (or headset) to MIKE AMPL

f. AVC Signal Gate Operation, Receive Mode.

OUT jacks (J6 and J12). Place the PTT switch to OFF.

(1) Set the SIDETONE GATE ADJUST

(2) Place the KEY switch on the test fixture to

control to obtain 7.0 + 0.1 volts at SIDETONE GATE

ON and record the voltage at MIKE AMPL OUT jacks

TEST jack (J3).

(J6 and J12). The output voltage shall not be less than

(2) Connect the audio oscillator and

3.5 volts peak-to-peak.

frequency counter to RCVR AUDIO IN jacks (J8 and

(3) Record the output frequency at jacks J6

J14), and adjust the output level to 0.1 volt at 1700 Hz.

(3) Note that the voltage at +AGC jack

(J10) decreases to not more than 0.5 volts dc and the

VOX ON lamp (DS2) lights when the KEY switch is

placed ON.

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