Bird Technologies 21-87A-11-xx-T Series-Manual - Manual (Page 20)

TX RX Systems Inc. Manual 7-9100-5 10/17/11 Page 14
Small movements of the main tuning rod are
facilitated by tapping the rod with the handle
end of a screw driver while gently pushing or
pulling the main tuning rod.
6) Lock the Main and Fine tuning rods and reinstall
the cavity in the system. Use the previously out-
lined fine tuning procedure to verify proper tun-
ing under power.
Retuning System To All New Frequencies
When retuning the combiner to all new frequencies
perform the following procedure in a step-by-step
fashion;
1) Determine new thruline cable lengths for the
new channels and the specific stacking order in
the rack. TX RX Systems Sales engineers will
assist by making the calculations using their
design software. Due to variations in coaxial
cable characteristics and assembly techniques,
factory supplied cables are recommended.
2) Use the Coarse Tuning procedure as outlined
earlier in this manual to tune each cavity chan-
nel to the new transmitter frequencies.
3) Connect the channels according to the new
Thru-line cable chart.
4) Fine tune each channel using the fine tuning
procedure as outlined earlier in this manual,
starting with channel 1 and proceeding to the
next higher channel. After tuning all channels,
repeat this step a second time to verify that
there is no more channel interaction.
5) Verify channel losses if desired using the multi-
coupler checkout procedure outlined previously.
MULTICOUPLER EXPANSION
Expansion channels for your multicoupler may be
ordered directly from TX RX Systems or its autho-
rized representative. The systems engineer will
help you select the right model and any required
options.
The expansion channel and options are shipped
with mounting instructions and a new T-Pass
Thruline cable sheet which shows the exact mount-
ing location of the new channel in the existing sys-
tem. In most cases, this channel will be added
directly to the next topmost position in the rack and
the antenna connection will then move to this cav-
ity. A new thruline cable will connect this channel
to the existing cavities.
The system engineer may also advise that the cav-
ity insertion loss on some of the existing channels
needs to be changed in order to accommodate a
new channel. This can be necessary when the new
channel is much closer in frequency separation to
existing channels than that previously encoun-
tered. This usually means increasing the cavity
loss for all close spaced channels which provides
the increased selectivity required. Cavity insertion
loss values are shown on the T-Pass Thruline
cable sheet.
Typical Expansion Channel Installation
The following text is a procedure for adding expan-
sion channel components to a typical T-Pass
Transmitter Multicoupler. Please keep in mind that
instructions shipped with the expansion compo-
nents supersede these procedures.
Typical Parts Included
(Quantity and Description)
(1) T-Pass Cavity Assembly.
(1) Single/Dual Isolator w/load on Mounting Plate
(1) 9.4" Isolator to Cavity Interconnect Cable
(4) Stainless Steel Band Clamps
(1) T-pass Thru-line Cable
(1) T-pass Thruline Chart.
PEG RACK PROCEDURE
1) Determine the location of the Expansion Chan-
nel in the rack by consulting the new
THRULINE cable chart.
2) Mount the cavity in the peg rack using two (2)
stainless band clamps, refer to Figure 10.
3) Rotate the cavity body so that the connectors
are orientated the same as those on the other
cavities and that no cavity-end cap screws are
preventing a flush fit with a mounting peg.
4) Tighten the cavity mounting clamps.
5) Attach the isolator mounting plate to the cavity
using two (2) band clamps. Clamp screws