Sunday, January 18, 2015

calibrating an rtl-sdr with PMR

The cheapness of the dvb-t style SDR comes with a price of it's own - an internal oscillator has not the highest possible precision and it's oscillating frequency tends to float a bit as the device gets warmer during an operation.

Thankfully there are ways to somewhat mitigate this issue in SDR software by setting the crystal's ppm offset. But how to determine the required value? Well, by comparing the SDR capture to something own like the PMR frequencies.
Via this simple method I found out the the freq. correction value for my dongle: -107 ppm.

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