Trying to measure the frequency variance of an RTL-SDR

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alien777
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Joined: Wed Aug 08, 2018 2:59 am

Trying to measure the frequency variance of an RTL-SDR

Post by alien777 » Wed Aug 08, 2018 9:59 am

My main goal is to test the stability of the RTL-SDR. Note: I am open to any other methods of testing stability. So I'm trying to measure the frequency variance of an RTL-SDR. How would I go about this? There are several routes I have heard of:

1) Doing the Allan variance. How would I go about this? What plug-ins/software is needed?

2) Analyzing the IQ band. It would be very nice to be able to generate something like this after recording a long time of IQ data:
https://www.rtl-sdr.com/wp-content/uplo ... plutus.png
But I'm not sure where to even start. First off, what is the best way to record the IQ without a monstrous file size, and second how would I graph it like in the image? Finally, how would I deduce variance from this?

Finally, I have one last question: what is the best way to save frequency-time data from and RTL-SDR? Also, any more recommendations about logging data from the software? I'm very new to this and very lost. Thank you for your time.

Edit: I'm using Windows. Also any tips on calibration? I just tuned into a local NOAA station and had to only adjust by like 2-3 ppm to calibrate. Seems...suspicious. I tried to use kalibrate but for some reason it didn't find any towers in the 800, 850, or 900 MHz range.

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