Bird Technologies 21-87A-11-xx-T Series-Manual User Manual

Page 27

TX RX Systems Inc. Manual 7-9100-5 10/17/11 Page 21

7) Temporarily connect the test leads from the

spectrum analyzer together through a UG-914
BNC union to set the zero reference.

8) Connect a UG-28 tee and a UG-57 coupling to

the T-Pass loop as shown in Figure 15.

9) Connect the test leads from the spectrum ana-

lyzer to the tee connector as shown in figure 15.

10) Adjust the cavities main tuning rod so that a

rejection notch appears in the center of the dis-
play.

11) Loosen the three loop locking screws and

rotate the loop to obtain the reference notch
depth from step 4.

The tightness of the locking screws
affects the depth of the rejection
notch slightly. It is usually necessary
to rotate the loop for a notch depth
that is slightly less than the reference.
The Notch depth will tend to increase
slightly as all three locking screws are
tightened.

12) Remove the bandpass loop and place it back

into the cavity with the connector-end up.

Procedure for Bandpass loop

1) The Bandpass loop should be installed with the

connector up and the ground point circle ori-
ented toward the center of the cavity as shown
in Figure 16.

2) Connect the test leads, with 10 dB pads

attached, to the spectrum analyzer; turn it on

NOTE

UG-28A/U

UG-57B/U

T-Pass
Loop

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.

Spectrum Analyzer

Bird SignalHawk

Signal Generator

Figure 15: Setting a T-Pass loop for a specific cavity insertion loss.