Battery operation

TM 11-6625-3017-14

lock-plate secured by two screws above the switch, slide

(5)

CRYSTAL switch.

Selects crystal required.

the switch button into its other position (as shown on the

Switch to OFF when not crystal controlled.

panel), reverse and replace the lock-plate to hold the

button in its new position. No other adjustment is

(6)

RANGE switch. Selects internal local oscillator

needed.

ranges as shown beside tuning dial, or external

oscillator.

Switch the MAINS -BATT switch Lo MAINS.

(7)

R. F. IN socket.

Type BNC.

Accepts signal

under test.

2.2.2

Battery operation

(8)

I. F. OUT socket. Type BNC. Connect to

counter for measuring carrier shift or to

The modulation meter also works on 24 V batteries. A

oscilloscope for viewing unfiltered a.m.

suitable supply would be a 24 V positive earth vehicle

envelope. Output is 1.5 MHz at about V.

battery, on or off charge. Negative earth systems must

not be used on any account, since the case of the

(9)

LEVEL control. Adjusts attenuation of signal

instrument and its coaxial connections would be live. If a

input at R. F. IN socket.

positive earth supply is not available, use dry cells. Six

4.5 V batteries, e. g. Exide type H30 or 3DT9, giving 27

(10)

SET A.M. level control. Adjust for SET reading

V initially, should give several hours of service before

on meter when Function selector is at SET A.

their output drops below 21.5 V. This is equivalent to

several weeks in normal use provided that the instrument

is switched off as soon as the measurement is

(11)

Function switch.

Selects setting up and

completed. Current drain is 350 mA approximately.

measuring conditions on f.m. and a.m. Numbers

Observe correct polarity when connecting batteries to the

show normal sequence of settings.

back panel terminals; left is positive.

(12)

A. M./DEV RANGE switch. Selects full-scale

Switch the MAINS-BATT switch to BATT.

meter range, six for f. m., two for a. m.

2.3 CONTROLS

(13)

MAX MOD FREQ switch. Selects modulation

bandwidth in f.m. measurements.

The following outline of control functions is intended

for reference purposes. Until you are familiar with the

(14)

OUTPUT terminals.

Provide demodulated

instrument, use the operating procedures detailed in later

output for connection to extra-sensitive meter,

sections.

wave analyser etc.

(1) Oscillator tuning dial. Shows effective internal local

(15)

Meter. Reads % a.m. depth and f.m. deviation.

oscillator frequency.

R.F. LEVEL arc applies to position 1 of Function

switch, and SET mark to the four SET positions.

(2) OSCILLATOR TUNE controls. (Outer: coarse - inner

: fine). Adjust for dial reading 1.5 MHz above signal

(16)

SET CAL F.M. preset. Standardizes deviation

frequency. Inoperative when using external local

measuring accuracy. Adjust for SET reading on

oscillator.

meter with Function switch at SET CAL.

(3) CRYSTAL sockets.

Accept style D miniature

(17)

DE-EMPHASIS switch. Applies deemphasis to

crystals for local oscillator control.

demodulated signal at OUTPUT terminals.

Does not affect meter readout, except on 1.5

kHz deviation range.

(4) EXT OSC socket. Type BNC: Accepts external

local oscillator signal of about 100 mV.

(18)

SUPPLY switch. Shows red segments when on.

Works on both mains and battery operation.

2-2