VOR RADIAL ACCURACY PERFORMANCE TEST.

TM 11-6625-2975-40

2-9. 9960 FM DEVIATION PERFORMANCE TEST. (CONT)

PROCEDURE

1. Enter frequency 108.00 MHz into test set,

2. 9980 FM TONE SELECT key is lit. Extinguish all other TONE SELECT keys.

3. Set oscilloscope controls as follows:

TIME BASE: Division A, 0.1 ms; Division B, 10 s

VERT: 0.5 volts/div

4. Center sine wave on oscilloscope and adjust trigger level control to start sine wave at horizontal

graticule centerline.

5. Adjust oscilloscope delay time multiplier control so that fifth cycle is displayed.

6. Press oscilloscope B DLYD pushbutton. Width of jitter at end of fifth cycle should be between

46.1 and 50.9s. If not, go to troubleshooting chart 2-1, sh 8.

NOTE

The width of the jitter is proportional to the 9960 Hz FM. A 9960 Hz signal deviation 480

Hz varies between 9480 and 10,440 Hz. The period of 10,440 Hz is 15.785 s and the

time for five cycles is 478.925s. The period of 9460 Hz is 105.485 s and the time for

five cycles is 527.425 s. The difference between them (527.425 s minus 478.925 s)

is 48.5 s. For a tolerance of 480 Hz 5 percent deviation, the width of the jitter must be

48.5s 5 percent ( + 2.4 s).

2-10. VOR RADIAL ACCURACY PERFORMANCE TEST.

TEST EQUIPMENT REQUIRED: RF Cable RG-58/U

Zifor, Collins Model 478A3

EQUIPMENT SETUP: Connect test set to 115 vac power source.

Connect zifor to test set as indicated in the following diagram.

EL9LY016

Turn on equipment. Allow at least 30 minutes for warmup.