[time-nuts] OT: Spectrum Analyzer

[Didier Juges]

Another major difference between the older (sweeping) analyzers and the more modern ones (FFT) is that the sweep type analyzers only look at one particular frequency once per sweep, and for a short time, while the fft types pretty much look at the entire span continuously. That makes the fft type much more capable of identifying low duty cycle transmitters. If the signals you are interested in are CW, it will not make much difference, but that is not always the case.

Didier KO4BB

------------------------ Sent from my BlackBerry Wireless thingy while I do other things... 

-----Original Message-----
From: Brooke Clarke <brooke at pacific.net>
Date: Sat, 31 Oct 2009 13:03:29 
To: Discussion of precise time and frequency measurement<time-nuts at febo.com>
Subject: Re: [time-nuts] OT:  Spectrum Analyzer

Hi Brent:

Spectrum analyzers can be used in different ways.  For example if you know 
there's a signal and want to characterize it.  The other case is where you're 
looking for some unknown signal that may be (or may not be present) down near 
the noise threshold.

The first case is straight forward and any of the modern analyzers will do a 
good job.  In the search case analyzers like the HP 70,000 series or the 4395A, 
4396A/B can search orders of magnitude faster than conventional units.
http://www.prc68.com/I/4395A.shtml

Note that the 4395A uses a 12 MHz wide analog IF feeding a fast DSP based 
receiver.  This allows things like a real 1 Hz IF bandwidth and also allows 
real power [SQRT(I^2 + Q^2) detection].  All analog SAs use peak detection 
since they have no way of detecting power.

Have Fun,

Brooke Clarke
http://www.prc68.com

Brent Gordon wrote:
> I'm thinking of buying a spectrum analyzer and would like to know what 
> Time Nuts recommend.  My requirements are fairly simple:
> 
> 3GHz Max frequency or higher
> Either GPIB or Ethernet interface for control and data capture
> Not much larger than an average desktop computer.  Portable is nice but 
> not necessary.
> Preferably under $3000.
> 
> I thought about building Scotty's Spectrum Analyzer or Poor Man's 
> Spectrum Analyzer, but decided I would rather buy one then build one.
> 
> I have an HP 141T but I am looking for something more modern.  One of my 
> uses will be looking at C and Ku band satellite signals (down converted 
> to 950-2050 MHz).  I'll also be using it to look at various RF data 
> links from 433 MHz to 2.4 GHz.
> 
> Thanks,
> Brent
> 
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