Formulas & Data:
- Electronics
- Mathematics
- Physics
- RF & Microwaves

Parts Vendors:
- all hand-selected

- Amateur Radio
- Vintage Articles:
- Electronics World
- Popular Electronics
- Radio & TV News
- Radio Craft
- Short Wave Craft
- Wireless World

- Events Calendar
RF Cafe Homepage
Copyright 1999-2015   •−•  ••−•    −•−•  •−  ••−•  •   "RF Cafe" in Morse Code  >> Listen to It <<
- EW & Radar Handbook
- Quizzes       - Software
- App Notes
- Calculators
- Advertise on RF Cafe
- About RF Cafe™
- RF Cafe Shirts & Mugs
- RF Cafe Archives
RF Cafe Book Contest
- RF Cafe on Visit RF Cafe on Facebook Visit RF Cafe on Twitter Visit RF Cafe on LinkedIn
- Tech Humor
- Forums Archive
- Job Board
- Donate to RF Cafe
- Kirt's Cogitations
Custom Search
More than 10,000 searchable pages indexed.
Greetings: There is so much good stuff on RF Cafe that there is no way to list or link to all of it here. Please use the Search box or the Site Map to find what you want - there is a good chance I have it here. Thanks!

Why is there a peak at 0 Hz on Spectrum Analyzer - RF Cafe Forums

Because of the high maintenance needed to monitor and filter spammers from the RF Cafe Forums, I decided that it would be best to just archive the pages to make all the good information posted in the past available for review. It is unfortunate that the scumbags of the world ruin an otherwise useful venue for people wanting to exchanged useful ideas and views. It seems that the more formal social media like Facebook pretty much dominate this kind of venue anymore anyway, so if you would like to post something on RF Cafe's Facebook page, please do.

Below are all of the forum threads, including all the responses to the original posts.

 Post subject: Why is there a peak at 0 Hz on Spectrum Analyzer
Posted: Mon Dec 18, 2006 11:11 am 

Joined: Mon Apr 03, 2006 4:06 am
Posts: 8
I am using a spectrum analyzer that has a measurement range from 9kHz up to GHz. When chosing a Start freq at 0Hz and span of 100 MHz, I see a peak from 0 Hz although I don't measure anything (Open).
Has this something to do with the VBW Filter?
I have seen this quite often but never have been asked about this...
Can someone give me a convincing explaination?
Thanks for any hint.

R&S RF Application Engineer

 Post subject:
Posted: Thu Dec 28, 2006 12:46 pm 
User avatar

Joined: Thu Apr 13, 2006 9:53 am
Posts: 17
Location: Florida
The response at 0 Hz is due to the Spec-Ana's LO feedthru. Read Aglient's application note AN150, Spectrum Analyzer Basics for the details.

Godd luck,

 Post subject:
Posted: Sun Jan 14, 2007 3:11 pm 
User avatar

Joined: Thu Jan 11, 2007 12:59 pm
Posts: 16
Long time ago since I was at school, but isn't the mathematical explanation that the fourier transform has "problems" with 0Hz?


 Post subject:
Posted: Fri Jan 19, 2007 7:55 am 

Joined: Thu Jan 18, 2007 8:09 am
Posts: 12
Location: Belgium
It's not really a "problem", but the Fourrier transform of a 0 Hz signal (direct signal) gives a Dirac Pulse at 0 Hz. If I remember well.

The agilent document given by RFTEJerry is very good to well understand the functioning of a spectrum analyzer.

Posted  11/12/2012

Your RF Cafe
Progenitor & Webmaster

Click here to read about RF CafeKirt Blattenberger… single-handedly redefining what an engineering website should be.

View the YouTube RF Cafe Intro Video Carpe Diem!
(Seize the Day!)

5th MOB: My USAF radar shop

Airplanes and Rockets: My personal hobby website

Equine Kingdom: My daughter Sally's horse riding website