Adjustments are done within a built-in service package. They are not part of the N7874A calibration application. Refer to the VNA documentation.
The VNA has three main adjustments:
Receiver Adjustment (Mixer Cal)
Since the modules are not repairable, they will need to be replaced if these adjustments do not solve the problem.
The following table shows which adjustments to run should a performance test fail. After running the adjustment, repeat the performance test. If it fails again, replace the module.
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If this test fails, |
do this adjustment: |
Comments |
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10 MHz Frequency Reference |
Use a known good-quality frequency counter, preferably in conjunction with a house reference. |
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|
Power Level Adjustment |
Use a known good-quality power meter and power sensor. |
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Receiver Adjustment (Mixer Cal) |
If any performance test should fail, you should first:
verify that your test connections are correct by referring to the test topic page.
ensure the equipment connections are torqued to proper specs.
check the input and output connectors on the test equipment for damage.
check cables and adapters for damage.
Issues with any power flatness holes or match could be caused by a damaged test port connector. Both test port connectors (3.5mm), and the two SMA LO connectors are user-replaceable. Refer to the service manual for more information.
This calibration is dependent on good connections using good a quality cable, adapter, and attenuator. If the adapter/cable/attenuator setup has been disturbed or disconnected between tests, then the PNAasPowerMeter calibration will need to be repeated. Although the calibration and test may pass even if the adapter/cable/attenuator setup has been disturbed or disconnected, the test results may not be as accurate.
Because the data from the PNAasPowerMeter calibration is stored and re-used by other tests, it is important that the most accurate data is achieved by following these practices.
TME will present a prompt that offers the user the choice to perform the calibration before starting the test at hand even if it's been within the allowed timeframe. Existing data can be used, if available. For troubleshooting, it is recommended to re-do the calibration especially if you are unsure if the adapter/cable/attenuator setup has been disturbed or disconnected.
This test has many dependencies which can lead to test failure or abort the test. These are thoroughly explained in the test's topic page.