HP 8596E full sweep

[Xtremexp]

Hello everyone,

I recently acquired hp 8596E and when i do full sweep i see this screen, which i think not normal. Any idea or clue what might be wrong or is it expected?
 
when I feed signals at 6G, 12G, the signal amplitude shows fine on the analyzer.


Regards,
Xtremexp

[Bud]

Did you check it against the datasheet specifications?

[tggzzz]

It is difficult to determine, because you have cropped important information displayed on the screen.

I would look at the various bands; 6.4GHz might be on a boundary. Higher bands have higher noise floors.

256ms is a fast sweep. What is the display with a slower sweep.

[max-bit]

Go to the website :
https://xdevs.com/doc/HP_Agilent_Keysight/08590-90316.pdf
Page :387

There you have an analyzer block diagram
I would bet damage to the block:
- A3A2 or A3A6 with the higher probability that it is the latter.

[Bud]

The full sweep screenshot was done with 3MHz rezolution bandwidth. What resolution bandwidth was used when you tested at 6GHz and 12 GHz? You have to compare apples to apples . The larger the resolution bandwidth the higher the noise floor. Datasheet gives specs at 30Hz resolution bandwidth. You have to set 30Hz RBW and check the noise floor against the specs. But you may not be able to set such small RBW in full sweep mode, or if you can then it will take a very long time for a sweep to complete.

[max-bit]

But not that noise level!

[MarkL]

I would try turning off corrections to determine if the raised noise floor is something gone awry during self-cal.

CAL --> More --> CORRECT OFF

[Bud]

@OP: evaluate your device as per the conditions indicated in the specification screenshot, then we will talk.

[Xtremexp]

I would try turning off corrections to determine if the raised noise floor is something gone awry during self-cal.

CAL --> More --> CORRECT OFF

Thanks Mark, when I turn off the correction the amplitude becomes flat as shown below. I did self cal several times but it did not help. what might the issue? I am taking measurements as others suggested at meantime.

when CORR is ON:


when CORR is OFF:


Many Thanks!

[MarkL]

What's odd is that only Band 2 seems to be having the unusual noise floor.  It's normal to have a jump in the noise floor going to Band 2, but it's usually less than 10dB and I don't think I've ever seen such variation.  Check against the specs as Bud suggests, but it doesn't look right to me.

Did you run the YTF calibration routine also?  Note that this uses the COMB output and not the CAL output.  I would also try re-running the regular self-cal after you've done the YTF cal.

There is a section in the Assembly-Level Repair Manual (see ref above from max-bit) that has some troubleshooting steps for this exact issue.  See "If the analyzer displays a high noise floor" on page 234.

The noise floor appears high because during calibration the cal signal was low and the calibration routine increased the system gain to compensate.  When you turn off the correction factors, those gain factors are removed.