Windowing Loss---not really

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Aerowerx
Posts: 4
Joined: Sun Dec 02, 2018 1:13 am

Windowing Loss---not really

Postby Aerowerx » Sun Dec 02, 2018 1:33 am

Hello, all!

I just joined this forum. Today I ordered an RSP-1a and downloaded both the spectrum analyzer and SDRuno software. Of course, I can't do anything with it yet.

I have been a ham for 50 years next month, and have always been disappointed at the poor quality of affordable test equipment for the home experimenter. Even way back then I new that somehow a computer with A/D and D/A converter could be used to replicate "real" test equipment. The time has finally arrived to fulfill my dream!

About 20 years ago I was writing software algorithms for a commercial product that was a computerized RF test system. This included creating a spectrum analysis routine and gathering as much information as possible on the signal.

i would like to point out that nothing is 'lost' by using a FFT window function. Instead the power is spread out over several bins, with the number of bins being determined by the particular window function. By summing the power in those several bins the result will be the actual power in that spectral line.

There were a number of other 'tricks' I devised, but I can no longer recall the details.

Jim
N8EE
Last edited by Aerowerx on Thu Jan 01, 1970 12:00 am, edited 0 times in total.
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SteveAndrew
Posts: 123
Joined: Thu Nov 16, 2017 11:06 pm
Location: Gold Coast, QLD, Australia

Re: Windowing Loss---not really

Postby SteveAndrew » Sat Dec 08, 2018 10:54 pm

Aerowerx wrote:i would like to point out that nothing is 'lost' by using a FFT window function. Instead the power is spread out over several bins, with the number of bins being determined by the particular window function. By summing the power in those several bins the result will be the actual power in that spectral line.

Hi JIm

You are correct, and this is one of the reasons I have not applied any "correction" for the slight differences in amplitude observed between different window types. I mentioned this briefly in the instruction manual, and included a link to an article that explains windowing in some depth.

http://download.ni.com/evaluation/pxi/U ... dowing.pdf

Best regards

Steve

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