PREPARATION FOR USE

TM 11-66253017-14

TABLE 2.1.

2.4 PREPARATION FOR USE

Frequency ranges

It is helpful in reading these instructions and in using

the instrument until completely familiar with its operation,

to remember that where a control or switch position is

RANGE switch

Range

Osc. freq.

R.F. input freq.

marked SET, the control should be adjusted to make the

setting

MHz

meter read on the line marked SET.

1-2

5.5 -11

4.0 - 9.5

Before commencing measurements:

11 - 22

9.5 - 20.5

3-4

22-44

20.5 - 42.5

(1)

Check the mechanical zero of the meter and

44.-.88

42.5 - 86.5

adjust, if necessary, by means of the screw.

5-8

88-176

86.5 - 174.5

176- 352

274.5 - 350.5

(2)

Turn the LEVEL control towards minimum

352-704

350.5 - 702.5

(counter-clockwise).

701.5-1001.5

700 - 1000

(3)

Connect the signal to be tested to the R. F. IN

EXT

F+ 1.5

socket at a level which, operating into50 1, will

develop a voltage within the limits given in

(4)

Set the oscillator RANGE switch in accordance

section 1.2 under 'R. F. input' .At the highest

with table 2.1. For detailed instructions on

carrier frequencies the shortest possible input

oscillator arrangements, see section 2.10. In

lead should be used or an external 50 f matching

this section, it is assumed that the internal local

attenuator.

oscillator will be used.

CAUTION Inputs greater than 3 V r. m. s. May damage

(5)

Set the Function switch to TUNE OSCILLATOR

the attenuator. If in doubt, use an external attenuator.

AND ADJUST LEVEL. Adjust the OSCILLATOR

TUNE dial to a frequency 1.5 MHz above the

carrier. Tune for peak meter deflection, and

(4)

Turn the SUPPLY switch clockwise so that the

then adjust LEVEL for a meter deflection in the

red segments show.

black R. F. LEVEL arc, preferably near the top

end for best signal-to-noise ratio.

(6)

Set the Function switch to F.M. SET FREQ.

2.5 MEASURING F.M. DEVIATION

Slightly readjust the OSCILLATOR TUNE control

until the meter deflects to the SET line. Avoid

After carrying out the preparation procedure in

spurious settings - the correct one is the closest

section 2.4:

to the original setting obtained in (5).

(1)

Set the A.M. /DEV RANGE switch (below the

(7)

Set the Function switch to DEV + and DEV-.The

meter) to suit the expected deviation of the

demodulated peak frequency deviations above

signal under test.

and below the carrier frequency may be

measured on the meter or viewed on an

(2)

Set the MAX MOD FREQUENCY switch to 200

oscilloscope connected to the OUTPUT

kHz unless the modulating frequency is less than

terminals.

Read the meter on the scale

15 kHz. If so, switch to 15 kHz in order to obtain

corresponding to the setting of the A. M./ DEV

the best signal-to-noise ratio.

RANGE switch.

(3)

Set the DE-EMPHASIS switch as required. Its

Note

If unequal readings are obtained, distortion in the

setting has no effect on the internal meter

equipment under test is indicated.

reading unless the A.M. /DEV RANGE switch is

See section 2.12.

in the 1.5 kHz deviation position. The de-

emphasis is effective on the demodulated signal

(8)

Before carrying out a series of measurements,

at the OUTPUT terminals.

and from time to time during measurements,

2-4