Author Topic: Need help with HP 8591A Spectrum Analyzer  (Read 542 times)

0 Members and 1 Guest are viewing this topic.

Offline e_glu

  • Newbie
  • Posts: 1
  • Country: ru
Need help with HP 8591A Spectrum Analyzer
« on: September 16, 2019, 07:22:47 pm »
Hi everyone!
I've always dreamed of my own spectrum analyzer, and I got a HP 8591A quite cheap today.
It's quite old, but clean and it works. Kind of.
It has a strange curve from 9 to about 100 KHz with no input cable attached, and calibration does not fix it. Please see the photo below.
Anywhere from 100KHz to 1.8GHz, everything is flat and fine.
Any suggestions, what can this be and how to fix that?
Thanks!
Evgeny
« Last Edit: September 16, 2019, 07:27:31 pm by e_glu »
 

Offline rf-loop

  • Super Contributor
  • ***
  • Posts: 3279
  • Country: cn
  • Born with DLL21 in hand
Re: Need help with HP 8591A Spectrum Analyzer
« Reply #1 on: September 17, 2019, 06:42:51 am »
Hi everyone!
I've always dreamed of my own spectrum analyzer, and I got a HP 8591A quite cheap today.
It's quite old, but clean and it works. Kind of.
It has a strange curve from 9 to about 100 KHz with no input cable attached, and calibration does not fix it. Please see the photo below.
Anywhere from 100KHz to 1.8GHz, everything is flat and fine.
Any suggestions, what can this be and how to fix that?
Thanks!
Evgeny

I think only what you need fix is your knowledge about what is SA and how it works.

Think RBW filter shape.  You use 3kHz RBW.  Its width is 3kHz, and it means this width is -3dB from center top.  I do not know just this model RBW filter shape factor but because it is full analog IF SA it may be example around 12:1  what means its width is 12x3kHz (36kHz (18kHz from center))   -60dB from top.

What you see is mostly like 0 Hz "image" after 3kHz RBW filter.
If you can (I do not remember sure this model), set start to 0Hz you see it more clear...(if you can set "negative" start freq, set example -20kHz.. you see this 0Hz (this is how SA work)


This is good to read basic fundamentals about SA's:
Spectrum Analysis Basics Application Note 150
Keysight Technologies



This OLD  AN-150  is nice to read also. Look page 13.  Do you have more narrow RBW filter than 3kHz, I think there is also 1kHz?

http://hpmemoryproject.org/an/pdf/an_150.pdf

(there is also more : http://hpmemoryproject.org/news/an150/an150_page_00.htm )



« Last Edit: September 17, 2019, 06:56:44 am by rf-loop »
If practice and theory is not equal it tells that used application of theory is wrong or the theory itself is wrong.
-
Harmony OS
 


Share me

Digg  Facebook  SlashDot  Delicious  Technorati  Twitter  Google  Yahoo
Smf