User's Manual

TB9300 Installation and Operation Manual Installation 83
© Tait Limited June 2016
5. Change the RF input signal to the new receive frequency at
–80dBm. Check that the RSSI reading is –80dBm ±1dB. If it is, the
receiver front end does not require tuning. If it is not, go to the next
step.
6. Using the Johanson tuning tool
1
, adjust the helical filter for the new
frequency (as shown in Figure 5.4) to obtain a peak RSSI reading.
This reading should be within 1dB of the reading at the previous
frequency.
Adjust the center resonator of the filter first, followed by the two
outer resonators (in any order). Each resonator should require
approximately the same amount of adjustment when tuning.
If tuning to a lower frequency, adjust the slug in (clockwise); for a
higher frequency, adjust the slug out (counterclockwise).
7. Change the RF input signal and the reciter’s receive frequency to
2MHz above and below the required frequency and check that the
RSSI reading does not drop by more than 0.5dB from the reading at
the required frequency.
8. Recalibrate the RSSI at the new frequency (Calibrate > Reciter >
RSSI).
If you wish to confirm the accuracy of the tuning procedure, carry out a
sensitivity measurement at the new frequency.
Electronically
Tuned Reciters
The G-band, K-band and L-band reciters do not require tuning.
1. Included in the TBA0ST2 tool kit. Also available separately as part num-
ber 937-00013-00.