The intent of this test is to verify that the LO Nulling adjustment is working properly. LO Nulling is performed in both the Field Adjustments and the Self Alignment routine. LO feedthru occurs when the signal analyzer is tuned to 0 Hz. At 0 Hz, the LO is the same frequency as the first IF. When the LO is at the IF frequency, the LO power blasts down IF chain and is detected. The LO nulling circuity beats the LO against itself (in opposite phase) to cancel this feedthru signal. The LO Nulling routine adjusts the phase for the optimal nulling.
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Test Equipment |
Recommended Models1 |
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50 W terminator |
909D Opt 301 |
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Frequency reference module |
M9300A |
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