Performing In-Band Power Meter User Calibration - Motorola GTR 8000 Manual

GTR 8000 Base Radio

5.11.2 Performing In-band Power Meter User Calibration

When and where to use:
The Aeroflex 3900 series HPD service monitor has two forms of power measurement:
• Broadband, which is similar to the working of an in-line wattmeter.
• In-band, which is performed after the RF signal is down converted to baseband by a DSP.
If the HPD service monitor runs continuously, it requires periodic calibration. Re-calibration is required only if
the User Calibration Threshold is exceeded. The service monitor displays a flag at the bottom indicating that
re-calibration is needed to maintain the accuracy indicated in the User Calibration Threshold.
For an HPD signal, only the in-band power meter is available. The in-band power measurement accuracy without a
user calibration is ±1 dB. User calibration improves the accuracy at a specific frequency, bandwidth, and temperature
by using the broadband power meter to correct the in-band power measurement. This correction occurs when
an in-band user calibration is performed.
Procedure Steps
Press the UTILS button on the service monitor twice.
1
Wait for approximately 1 second or more before pressing the UTILS button the second time.
Step result: The Utility Menu screen appears.
2 Select User Calibration from the drop-down menu.
Step result: The User Calibration screen appears.
3 Click the Run User Calibration button located at the upper right corner of the User Calibration screen.
The default user calibration setting is 1.0 dB. This means the HPD service monitor will not indicate a user
re-calibration until the in-band power measurement has a potential of 1.0 dB error in the measurement
(same as the basic in-band power meter accuracy). For HPD, a 0.5 dB value or lower is more appropriate.
This may require more frequent user re-calibrations, but it provides better performance.
Step result: A User Calibration message box appears asking you to remove all connectors from the ports.
4 Remove all connectors from the ports. Click Continue.
Step result: A progress bar appears showing the progress of the calibration process. The calibration completes
in approximately two minutes.
Failure to remove all connectors and cables from the ports causes an inaccurate user calibration. Any
connectors present causes a variation on the impedance seen by the instrument during calibration.
5-48 6871022P86-A - November 2012