TB 9-6625-2076-24
11. Modulation, Tone Frequency
a. Performance Check
NOTE
Since all of the audio tones are derived from the same reference
crystal, only the accuracy of one tone is checked.
(1) Connect frequency counter to TI COMP (rear panel).
(2) Enter a frequency of 108.000 MHz into TI and press TONE SELECT 9960 Hz
pushbutton (all other TONE SELECT pushbuttons off).
(3) Measure period of 9960 Hz tone. Frequency counter will indicate between
100.39658 and 100.40662 s. If not, perform b below.
b. Adjustments. Adjust A2A3C7 (located on left side of TI, top front of board A2A3)
for a 100.4016 s frequency counter indication (R).
12. Modulation Tone Distortion
a. Performance Check
(1) Connect audio analyzer to TI COMP (rear panel).
(2) Set TI frequencies and TONE SELECT key to settings in table 7. Measure
distortion using standard measurement techniques. Audio analyzer will indicate within
limits specified.
Test instrument
Audio analyzer
maximum distortion (%)
Frequency
Tone select
(MHz)
key
108.00
9960
Hz
0.5
108.00
1020
Hz
0.5
332.00
90
Hz
0.25
332.00
150
Hz
0.25
75.00
400
Hz
1.0
75.00
1300
Hz
1.0
75.00
3000
Hz
1.0
b. Adjustments. No adjustments can be made.
13. FM Deviation (Zero Beat Method)
a. Performance Check
(1) Position oscilloscope controls as listed in (a) through (k) below:
Press Default Setup.
(a)
Select Graphical Interface
(b)
Set Channel 1 and Channel 2 to 500mV/.
(c)
Select Analyze menu, Math/FFT, and set Operator to Versus.
(d)
Set Source 1 to Channel 1, Source 2 to Channel 2.
(e)