Bird Technologies 21-87A-11-xx-T Series-Manual - Manual (Page 24)

TX RX Systems Inc. Manual 7-9100-5 10/17/11 Page 18
tors for the Reference Notch Depth Value
shown in the chart (table 4) for the desired
insertion loss and T-Pass loop part #.
2) Connect the test leads together through the
female union, as shown in Figure 12, and
adjust the range switch and the zero set on the
voltmeter for a convenient reference level (A
level of 2 on the 0 to 3 scale for example) on the
meter. The generator output level may also be
adjusted slightly if necessary.
3) Remove the bandpass loop from the cavity and
insert it, connector end first, back into the cavity
and tighten all 3 screws securely. See Figure
13.
4) Set all three attenuators for 0 dB but leave them
in the circuit.
5) Connect a UG-28A/U Tee connector and UG-
57B/U coupling to the T-Pass loop as shown in
figure 13. Then connect the test leads as
shown. Make sure to install the short circuit stub
(part # 3-2330) from the top of the T-Pass rack
if the loop does not have an internal short.
6) Loosen the main tuning rod locking screw and
slowly slide the tuning rod in or out to obtain a
dip (minimum voltage) in the meter reading
which indicates cavity resonance. Use the fine
tuning control to maximize the dip (the fine tun-
ing rod should not be full in or out which would
indicate that slight adjustment of the main tun-
ing rod is necessary). Note the meter reading.
7) If the meter reading is greater or less than the
reference level from step 3, the T-Pass loop
rotation will have to be adjusted. If the meter
Modulated
Signal Source RF Voltmeter
Rotary Attenuators
Set to Loop Reference Settings
0.1 dB/Div. 1.0 dB/Div. 10 dB/Div.
50 Ohm Adaptor
UG-28A/U
UG-57B/U
T-Pass
Loop
10 dB Pad 10 dB Pad
Short Circuit Connector
3-1268 from top of rack
Bandpass Loop turned upside down
with connector inserted into cavity.
Loop visible and screws tight.
Figure 13: Setting the T-Pass loop using step attenuators.