Frequency resolution scanning MW band

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WolfgangS
Posts: 1
Joined: Mon Nov 21, 2016 2:45 pm

Frequency resolution scanning MW band

Post by WolfgangS » Mon Nov 21, 2016 2:52 pm

Hallo,
my first post here in this forum. I owe the Red Pitaya since two weeks.

I use the inbuild spectrum analyzer software to scan the MW area (signal from my 100m² magnetic loop) from 450 to 500 kHz, and the frequency resolution is only 1 Khz.
Is there a way to change the resolution down to 1 Hz or at least 10 Hz ?

tu es 73, Wolfgang

Nils Roos
Posts: 1441
Joined: Sat Jun 07, 2014 12:49 pm
Location: Königswinter

Re: Frequency resolution scanning MW band

Post by Nils Roos » Mon Nov 21, 2016 11:04 pm

Hi Wolfgang,

let's start with the answer, which is 'no'.
Theoretically, the best frequency resolution that you can achieve within the constraints that the spectrum analyzer works with is about 100Hz.

At 500kHz you need a sampling frequency of at least 1MHz. The closest sample rate that the scope logic - which provides the samples for analyzing - supports is 1.95MSps. The scope can record 16384 samples at most. My DSP math is a bit shaky, so I may be off by a factor of 2, but at this rate and this window size, a Fourier transform can do no better than 120Hz resolution (might be 240Hz).

Now, if you were to design your own spectrum app, you could try to use a method to record more samples at once and get a better resolution by way of the larger window size ...

chuerta
Posts: 11
Joined: Fri Nov 20, 2015 10:01 pm

Re: Frequency resolution scanning MW band

Post by chuerta » Sat Apr 01, 2017 11:46 pm

I understand if I use Labview those constraints for the Spectrum Analyzer are different, there is 256MB available to buffer data and then Labview to produce the Spectrum with bins at less than 10Hz, is that right?

Thanks

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