Author Topic: Erroneus trace on my HP 3585A Spectrum Analyser  (Read 616 times)

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Offline John_SinhaTopic starter

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Erroneus trace on my HP 3585A Spectrum Analyser
« on: December 14, 2022, 04:07:52 pm »
I recently purchased this old spectrum analyser off eBay for a few quid. What is causing this erroneous trace. I have nothing connected to the input of this spectrum analyser. Any idea why the response is not flat at the low end (under 900Hz)?
« Last Edit: December 14, 2022, 04:09:56 pm by John_Sinha »
 

Offline jonpaul

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Re: Erroneus trace on my HP 3585A Spectrum Analyser
« Reply #1 on: December 14, 2022, 04:32:39 pm »
normal, no problem!

Baseline displays noise floor, see specifications.

Large peak at left is mixed 0 Hz, every Analyzer has similar


read up on sweep mixer lo type RF Analyzer theory, many HP applications notes

get manual

j
« Last Edit: December 14, 2022, 06:14:02 pm by jonpaul »
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Offline 807

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Re: Erroneus trace on my HP 3585A Spectrum Analyser
« Reply #2 on: December 14, 2022, 06:11:31 pm »
Yep. It's called the "zero response". Just a 0Hz marker aligned with the left hand side of screen. It's mentioned on page 3.2.1 & a few other times in the manual.

https://pearl-hifi.com/06_Lit_Archive/15_Mfrs_Publications/20_HP_Agilent/01_HP_3585A-B_40MHZ_SpecAn/HP_3585A_Operating.pdf
 
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