Tait P25 CG User Manual - page 17
TB9100 Calibration Software User’s Manual
Adjusting the Frequency Setup 11
Use the tuning tools as follows.
a. Insert the Johanson tuning tool into the first hole of the first (horizontal)
set. You can start with the hole on the left side and proceed along to the
hole on the right, or vice versa. On K-band reciters, the third hole tends
to tune with the slug well out of the filter body. Be careful not to
unscrew the slug completely.
b. Tune each of the resonators in the first set once to give the best response.
c. Insert the Johanson tuning tool into the first hole of the second (vertical)
set. You can start with the top hole and proceed down to the bottom
hole, or vice versa. (For version 4.00 or earlier H-band reciters, use the
Murata tuning tool on this set instead, as instructed by the wizard.)
d. Tune each of the resonators in the second set once to give the best
response.
e. Repeat this procedure as necessary to refine the response.
5. Once you have roughly tuned the front-end helical filters, click Fine
(slow)
. Repeat the above procedure to fine tune the front-end helical filters
until the response is peaked in the middle of the lock band and not more
than -1 dB at the ends of the band.
Note:
When using the Fine (slow) setting, you may notice a slight
delay as the reading from tuning the front-end helical filters takes
approximately one second to appear on the graph.
6. Click Finish. An alert appears, asking that you calibrate the RSSI. The icon
on the Frequency Setup tab indicates that this task is complete.
7. Re-calibrate the RSSI (see
“Calibrating the RSSI” on page 18
).
Tuning a VHF Receiver Front End
The second step in tuning a VHF reciter is to tune the receiver front end, by
adjusting trimmer capacitors. Tuning aims to maximize the receiver’s sensitivity
and to optimize its response across the lock band (switching range).
To help you do this, there is a graph of the RSSI readings in step two of the
Tune Receiver Front End Wizard. A number of RSSI readings are measured
across the switching range. These readings are then continually averaged to
produce the graph.
Important:
After tuning the reciter front end, you must re-calibrate the RSSI.
This requires a signal generator.
Otherwise the value reported by the CSS will
be in error, RSSI gating levels will be incorrect in analog mode, and voting
will be inaccurate in both modes.
You should aim to achieve a response that looks something like this: