[Test-Equipment] Can a scope + FFT function as a SA?

[Fuqua, Bill L]

The problem with FFT is the filtering. If you want a to have a resolution bandwidth of 100 Hz you have to record a sample forat least 10 milliseonds.
If you are looking at 100 MHz that means you will have to have a record length of 2 Msamples minimum. Some digital oscilloscopes will not do that 
and it may take some time to do a 1Msample FFT.  If you want resolution bandwidth of 10 Hz then it will be 4Msamples minimum.
   If the software has a method to effectively mix the frequency on interest down to 1 MHz then you only need a record length of a 32kSamples (next power of 2 above 20kSamples).
Or you could mix down the signal yourself externally and perform the FFT.
  
73
Bill wa4lav

________________________________________
From: test-equipment-bounces at mailman.qth.net [test-equipment-bounces at mailman.qth.net] On Behalf Of J. Forster [jfor at quik.com]
Sent: Tuesday, December 28, 2010 10:07 AM
To: Discussion of Electronic Test Equipment
Subject: Re: [Test-Equipment] Can a scope + FFT function as a SA?

Yes. I have a low end Tek TDS1002 and it has a nice FFT/SA function. It's
not a high-end SA, but it sees the BC band and FM band just fine.

Best,

-John

=============> Can a scope with FFT function be used like a basic SA
within the
> bandwidth of the scope?
>
> Filtering and other nice features of a true SA cannot be had, of
> course, but to what extent can the FFT function be made to perform as
> a SA?
>
> Thanks,
> Dave
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