Transmit Power
Check the transmitter output power (see Monitoring > Radio ‘Transmitter Last TX Packet Forward Power’
on page 318). This value will be dependent on the output power setting, the ATPC setting, the temperature
and the VSWR of the antenna.
The actual average transmit power can be measured by using a spectrum analyser with average power
measurement capability. Connect the radio antenna output to the spectrum analyser input via an attenuator
of at least 30 dB.
Transmit Frequency
Check the base station radio transmit frequency according to your routine maintenance schedule. It is
recommended that this be done within two years of installation.
Aprisa SR+ software release 1.9.0 and later contain CLI commands to adjust the transmit frequency if
necessary.
This procedure requires a frequency counter with an accuracy of 0.1 ppm or better. Do not attempt this
adjustment without a counter of this stability.
Transmit Frequency CLI Adjustment Procedure:
1. Establish CLI connection to the radio see ‘Command Line Interface’ on page 390.
2. Turn on CW mode:
>> set testmodeTxCW 1
3. Measure the transmit frequency using a frequency counter connected to the radio antenna output
via an attenuator of at least 30 dB.
4. Turn off CW mode:
>> set testmodeTxCW 2
Note: The transmission may cease if the Test mode timeout value is less than the time to measure
the frequency. Increase the Test mode timeout value if necessary.
5. Calculate the frequency adjustment required in hertz.
6. Set the calibration adjustment in the format;
‘x’ for a positive adjustment e.g. ‘105’ for +105 Hz
‘-x’ for a negative adjustment e.g. ‘-241’ for -241 Hz.
>> freqtrack txcalibration set ‘x’
7. Repeat process from step 2 if required to achieve an error of less than 40 Hz.
Transmit Spectrum
Check the transmit output spectrum with a spectrum analyser. Look for any visible intermodulation
particularly in adjacent channels.
Note that adjacent channel power measurements require a laboratory grade spectrum analyser and cannot
be performed with field instruments.
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