TB 9-6625-2163
9. Receiver Bandwidth and Frequency
a. Performance Check
(1) Select Menu 10 and increase MAIN FREQ until TI REJECT lamp comes on.
Slowly decrease MAIN FREQ until ACCEPT lamp just lights and record frequency.
(2) Decrease MAIN FREQ until TI REJECT lamp comes on. Slowly increase
MAIN FREQ until ACCEPT lamp just lights and again record frequency.
(3) Determine center frequency by adding values recorded in (2) and (3) above and
dividing by 2. If TI center frequency is not between 1089.5 and 1090.5 MHz, perform b(1)
through (5) below.
(4) Determine bandwidth by subtracting value recorded in (2) from value recorded
in (1) above. If bandwidth is not between 5.5 and 7.5 MHz, perform b(6) through (13)
below.
b. Adjustments
NOTE
Be extremely careful when performing these adjustments because
they are critical to equipment performance. Steps (1) through (4)
below shall be used, if necessary, to peak the receiver frequency.
Steps (6) through (13) below shall be used only if the bandwidth is
not within limits.
(1) Disconnect cable from RTS oscilloscope CH 1 to DEMOD OUT connector and
connect oscilloscope CH 1 (using X10 probe in RTS accessory kit) to test point A8TP2 of TI
(2) On RTS select Menu 10 and set FREQUENCY to 1090 MHz.
(3) Loosen (slightly) locknut of TI FREQ ADJ control at preselector A15Z1 (fig. 2)
and adjust FREQ ADJ control until displayed pulse is peaked (R).
(4) Retighten FREQ ADJ control locknut, while using a screwdriver to maintain a
peaked pulse.
NOTE
Steps (3) and (4) may have to be repeated for optimum results.
(5) Repeat a(1) through (3) above.
NOTE
During factory calibration, a red mark may have been placed on
each jack to identify probe position. If these marks are not
present, start with (6) below. If the marks are present, start
with (11) below.
