70 Installation TB9300 Installation and Operation Manual
© Tait International Limited April 2024
4. Set the reciter to the new receive frequency.
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 correct helical filter for
the new frequency (as shown in Figure 4.3) 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.
A change in frequency of 5MHz requires approximately one turn of the
tuning slug. If tuning to a lower frequency, turn the slug clockwise; for
a higher frequency, turn the slug anti-clockwise.
7. Change the RF input signal and the reciter’s receive frequency to
0.5MHz 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).
H Band Before the base station is installed on site, you may need to tune the
receiver front end. The receiver front end requires tuning if the receive
frequency is shifted more than 5MHz away from the previously set
frequency, or the RSSI level of the new frequency is more than 1dB lower
than the RSSI level of the previously set frequency.
Tait can provide extender cables (TBC Reciter Power Cables) to enable
tuning with a subrack or from a bench power supply. To order these, the
part number is T01-01150-0001.
The receiver in the H band reciter covers one of the following frequency
sub-bands, depending on the model:
■ H1 - 400 to 440MHz
■ H2 - 440 to 480MHz
■ H3 - 470 to 520MHz
■ H4 - 380 to 420MHz
2
Each sub-band uses the same helical filter (shown in Figure 4.4 below).
The bandwidth of the helical filter is approximately ±5MHz.
1. Included in the TBA0ST2 tool kit. Also available separately as part
number 937-00013-00.
2. The H4 band variant has no helical filter, so does not require tuning.
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