TB 9-6695-263-35
Table 4. FM Accuracy
Test instrument FM limits (kHz)
Calibrator frequencies (Hz)
Min
Max
100,000
98.9
101.1
200,000
94.9
105.1
50
98.9
101.1
20
94.9
105.1
(8) Press HP FILTER 50 Hz and LP FILTER 3 kHz pushbuttons.
(9) Set calibrator for a wideband output frequency of 1 kHz and output level for a
50-kHz indication on TI display.
(10) Press MEASUREMENT AM pushbutton.
(11) Momentarily disconnect cable from calibration fixture AUDIO INPUT. Record
TI display.
(12) Reconnect cable to AUDIO INPUT and record TI display.
(13) Subtract one-half of value recorded in (11) above from value recorded in (12)
above. If result is not 0.2 percent or less, perform b below.
b. Adjustments
(1) Adjust calibrator frequency for 100 kHz.
(2) Set calibration fixture test mode switch to FM.
(3) Connect TI INPUT to calibration fixture FM OUTPUT.
(4) Press HP FILTER 50 Hz and 41.0 SPCL pushbuttons.
(5) Adjust calibration fixture carrier frequency to 400 MHz.
(6) Press INPUT FREQ MHz and MEASUREMENT FM pushbuttons.
(7) Adjust calibrator output level for a 400-kHz peak deviation on TI display.
(8) Alternately press DETECTOR PEAK + (positive) and PEAK - (negative)
pushbuttons while observing TI display. If indications are not equal in both positions,
adjust A18R23 FM DISTN 1.5 IF (fig. 1) for an equal indication on TI (R).
(9) Press 3000 kHz and + (down) pushbuttons.
(10) Alternately press DETECTOR PEAK + (positive) and PEAK - (negative)
pushbuttons while observing TI display. If difference between the two indications is not
less than 1.6 kHz, adjust Al8R23 again to diminish difference by one-half.
(11) Press ↑ kHz pushbutton. TI is properly adjusted when pk1+ = pk2- and pk1 =
pk2+.
(12) Connect calibration fixture FM 4 output to TI INPUT.
(13) Press LP FILTER
pushbutton
to
3
kHz
and
press
AUTOMATIC
OPERATION pushbutton.
(14) Adjust calibrator to 1 kHz and adjust amplitude level for 50 kHz peak deviation
on TI.
11
