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8590A Spurious signal on display

Question asked by phil_r on Nov 22, 2010
Latest reply on Dec 23, 2010 by tabbott
Hi All,
I am slowly bringing an old 8590A Spectrum analyser back to life. It is generally OK. Displayed signal levels are down by about 2dB (after self calibration), but that could be my signal generator.

I have a strong spurious response appearing on the display (at about 3MHz) when displaying 0...10MHz and a resolution bandwidth of 30KHz or less is selected.
Image
This disappears for resolution bandwidths of 100KHz or more
Image

Changing the sweep speed does not seem to change the location of the spurious.

In both pictures, the 5MHz -20dBm signal is from my signal generator.

I am unsure if the spurious is from a fault in the bandwidth filters, or maybe the YIG oscillator, or maybe a glitch in the DAC drive to the tuning coils.
Also, the zero spur seems pretty strong. Maybe I have a blown first mixer.

Does anyone have any thoughts?

Thanks in advance, Phil  

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