Main Spectrum Settings / FFT Window choices?

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Bud Raridon
Posts: 2
Joined: Sun Jul 23, 2017 3:52 pm

Main Spectrum Settings / FFT Window choices?

Postby Bud Raridon » Fri Apr 12, 2019 1:02 am

Hello Group, I am using an RSP-1 with SDRUNO V1.31. I am playing with the "FFT Window settings and not seeing much difference between the default setting and the other choices. I get that they are probably different ways to achieve the FFT function, and I'm not really interested in the "how" as much as the final different effect that each of the choices has on the FFT/Waterfall displays. Any help you guys can give me would be appreciated.
Regards,
BudR.
Last edited by Bud Raridon on Thu Jan 01, 1970 12:00 am, edited 0 times in total.
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g1hbe
Posts: 461
Joined: Sat Jan 17, 2015 3:28 pm
Location: Cheshire, UK

Re: Main Spectrum Settings / FFT Window choices?

Postby g1hbe » Fri Apr 12, 2019 8:09 am

A couple of obvious ones to kick off with - try changing the averaging to a higher value, you should see a 'smoothing' effect on the spectrum display and it will react more slowly too. This can be useful for seeing small signals in the noise.
The RBW (resolution bandwidth) is like the IF bandwidth in an analogue radio, if you set it to a very small value you can distinguish signals which are very close together. Making it bigger will combine two close peaks into one wide one and hide the detail.
Both these can be found on Spectrum Analysers as well. Not surprising really, as that's exactly what the Main SP is.
Lots more to fiddle with!

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Andy

Bud Raridon
Posts: 2
Joined: Sun Jul 23, 2017 3:52 pm

Re: Main Spectrum Settings / FFT Window choices?

Postby Bud Raridon » Sat Apr 13, 2019 4:23 pm

Thanks for the relply Andy, but what I was looking for was the effects made by the various FFT window choices:
Hann,
Blackman,
Hamming,
Sin ^3
Sin ^5,
Nuttall,
Flat Top P401,
Rectangular,
The default seems to be Sin ^3. I have tried each of the others and they don't seem to do much. Am I missing something that I should be doing in addition to the selection of each of these FFT methods? The choices must be there for a reason. Anyway, thanks to anyone who could shed a little light on this subject.
Regards,
BudR.
Last edited by Bud Raridon on Thu Jan 01, 1970 12:00 am, edited 0 times in total.
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sdrom33
Posts: 97
Joined: Sun Dec 09, 2018 4:38 pm

Re: Main Spectrum Settings / FFT Window choices?

Postby sdrom33 » Sat Apr 13, 2019 9:08 pm

Too long to explain go and get "understanding FFT and windowing" pdf, it is worth reading!

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