A.M. and l.f. response

TM 11-6625-3017-14

(2)

Connect the voltmeter to the OUTPUT terminals.

5.4.8

A.M. and l.f. response

Turn the DE-EMPHASIS switch to 75 sec, the

Test equipment: j and k

(3)

Function switch to DEV+ and the MAX MOD FREQ

(1)

On the a. m. detector unit (All) disconnect the links

to 200 kHz.

from pins 17 and 18. Then connect the signal

source between pins 18 and 10 (earth).

(4)

Set the signal source frequency to 100 Hz and

adjust its output level to give a suitable reference

(2)

Turn the % A. M. RANGE switch to 100% and the

deflection on the output voltmeter.

Function switch to A. M. PEAK.

(5)

Vary the signal source frequency, keeping the

(3)

Connect one voltmeter across the OUTPUT

output level constant, and check that the response

relative to the 100 Hz reference is within 1 dB of:

terminals and another to monitor the signal source

output.

-3 dB at 2. 1 kHz.

(4)

Set the signal source frequency to 10 kHz and its

-16.9 dB at 15 kHz.

output to give a reading of 100% on the TF 2300A

meter. Note the reference level on the output

(6)

Repeat step (5) with the DE-EMPHASIS switch set

voltmeter.

to 50 sec and check that the response is within L.

dB of:

(5)

Vary the signal source frequency, keeping the level

constant, between 30 Hz and 50 kHz and note that

-3 dB at 3. 15 kHz.

the reading on the output voltmeter is flat to within

-16.9 dB at 22.5 kHz.

0. 25 dB of the reference level.

(6)

Switch off the TF 2300A, remove the test

5.4.7

Range attenuator

equipment and replace the link between A11 pins

17 and 18.

Test equipment: j and k

5.4.9

Discriminator trigger

(1) Connect the signal source as in step (1) of

Sect. 5.4.6.

Test equipment: a

(2)

Connect the voltmeter to monitor the signal source

(1)

With the modulation meter switched off disconnect

output.

the lead from pin 2 on the discriminator unit (A5)

and connect the multimeter to the collector of A5Q2

(3)

Turn the DEV RANGE switch to 5 kHz and the DE-

(or Q3).

EMPHASIS switch to OFF.

(2)

Switch on and adjust A5RVl to a point where the

(4)

Set the signal source frequency to 1 kHz and adjust

circuit is at change of state, i.e. multimeter either

its output to give full-scale deflection on the TF

reads 0 V or 15 V. When the potentiometer is

2300A meter.

adjusted the voltage will jump either to 15 V or 0 V

from the original reading. Set to a position just

(5)

Turn the DEV RANGE switch to 15 kHz. Increase

before it jumps.

the signal source output by 10 dB and note that the

meter reads within 1l% of full-scale.

(3)

Transfer the meter to pin 7 (i. e. test point adjacent

to RV1). Note the voltage and decrease it by 0.5 V

(6)

Repeat step (5) for the 50, 150 and 500 kHz

by rotating RV1 counter-clockwise. Check that the

deviation ranges.

output waveform at the output terminals of the

instrument is free from spurious pulses. Switch off

(7)

Switch off the TF 2300A, remove the test

the TF 2300A and reconnect pin 2.

equipment and reconnect the yellow lead to the

discriminator output.

5-7