User's Manual

26 Calibrating the PA Power © Tait Electronics Limited 2005
Setup for Inline
Power Meter
Note: Cables and connectors can easily cause a power loss of several
watts if either too long or poorly terminated. Always use the
shortest possible leads (or connectors instead of leads) between the
PA and power meter set-up.
To calibrate the PA transmit power
1. Ensure that the Calibration Kit PC is connected to the base station.
2. Select the PA Calibration tab, and select Calibrate PA Power.
3. Ensure that the power meter and a 50 ohm load (VSWR < 1.2:1) with a
high power rating are connected to the power amplifier RF output, and
then click Next.
4. Check that the PA RF input is connected to the reciter RF output, and that
the PA and the reciter are connected by a control bus, and then click Next.
5. For each power level shown, use the slider to adjust the DAC setting to get
the required power output, and then click Next Power to move to the next
line.
Note: Click Coarse to roughly adjust the DAC setting, and once
you get within range, click Fine for more precise control over the
settings. To move up or down one DAC value, click either side of
the slider bar.
Note: You must perform the calibration in sequence from the lowest
to the highest step. The DAC setting must be greater than the
previous one otherwise the value will not be stored in the PA, and
you cannot move to the next line.
6. When you have completed adjusting the DAC settings, click Finish.
When you have finished, the icon on the PA Calibration tab indicates that
this task is complete.
Troubleshooting Tips
DAC Settings When you adjust the DAC settings, the values for the DAC Setting, Coupler
Fwd Voltage, and Control Voltage should always increase as the power level
increases. If these values do not increase, there is either a fault with the PA or
the previous step was not calibrated correctly. If you make a mistake in the
calibration table, you must start again from step 1.
Control Voltage The Control Voltage is shown in the table to indicate the operation point
within the power control loop. The range of the control voltage is from 0 V to
7.5 V. If the control voltage reaches its limit before achieving maximum power
in the table, this indicates either a faulty gain stage in the PA or low RF input
power to the PA.
1 3
2
4
5
1 Reciter 3
PA
5 Load
2 16-way cable 4 RF Power Meter