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.

This disappears for resolution bandwidths of 100KHz or more

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
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.

This disappears for resolution bandwidths of 100KHz or more

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
Even though the self calibration appears to be running and you are presumably storing that cal, there may be a goofy number in the cal table that is causing you problems. That cal routine will try to correct even when there is broken hardware. You will know this by a large correction value. Please review the attached and look over each number in the display cal data (Cal, More, More, Display Cal data…something like that), which will show typical cal values. When you change from a 100 kHz RBW to a 30 kHz RBW, the RBW filters change from an LC path to a crystal path. Maybe the crystal path is foo-bar and the filters need adjusting…or worse the hardware is broken altogether.
Interesting to that the L.O. feedthrough, basically your 0 Hz signal is way off the top of the screen. This is usually caused by a blown first mixer do to overpowering the front end.
Regards -
Relevant Products:#8590A#