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<body class='hmmessage'><div dir='ltr'>Ah, I think I should be looking at the stddev which is telling me<br>that the average deviation from the range was approx 3-4Khz...?<br><br><div><hr id="stopSpelling">From: n1gp@hotmail.com<br>To: osmocom-sdr@lists.osmocom.org<br>Subject: kalibrate-rtl results...<br>Date: Thu, 30 Jan 2014 13:21:43 -0500<br><br>
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<div dir="ltr">I'm attempting to calibrate my RTL dongles. I notice they are<br>all about 2-4khz off if I compare against a known broadcast<br>station's frequency.<br><br>I am trying out kalibrate-rtl and am getting varied results.<br>I am in the US, so I did a 'kal -s EGSM -g 20' and got the following:<br><br> chan: 991 (928.4MHz + 26.986kHz) power: 448020.99<br> chan: 1002 (930.6MHz - 5.631kHz) power: 320357.07<br> chan: 1003 (930.8MHz + 16.192kHz) power: 109489.92<br><br>Then 'kal -c CHANNELNUM -g 20' for each channel number.<br><br>I then get the results below which the average frequency error looks<br>different for each channel. It is consistent though if I run them multiple times.<br><br>I would have expected less frequency error since I know that it is really only<br>about 4Khz off. Or am I not reading the results correctly?<br><br>-Rick<br><br>Using device 0: Generic RTL2832U OEM<br>Found Fitipower FC0013 tuner<br>Exact sample rate is: 270833.002142 Hz<br>Setting gain: 100.0 dB<br>kal: Calculating clock frequency offset.<br>Using E-GSM-900 channel 991 (928.4MHz)<br>average [min, max] (range, stddev)<br>+ 21.342kHz [17837, 27433] (9596, 3402.206299)<br>overruns: 0<br>not found: 199<br>average absolute error: -22.988 ppm<br><br>Using device 0: Generic RTL2832U OEM<br>Found Fitipower FC0013 tuner<br>Exact sample rate is: 270833.002142 Hz<br>Setting gain: 100.0 dB<br>kal: Calculating clock frequency offset.<br>Using E-GSM-900 channel 1002 (930.6MHz)<br>average [min, max] (range, stddev)<br>- 11.529kHz [-15293, -5679] (9614, 3640.780273)<br>overruns: 0<br>not found: 194<br>average absolute error: 12.389 ppm<br><br>Using device 0: Generic RTL2832U OEM<br>Found Fitipower FC0013 tuner<br>Exact sample rate is: 270833.002142 Hz<br>Setting gain: 100.0 dB<br>kal: Calculating clock frequency offset.<br>Using E-GSM-900 channel 1003 (930.8MHz)<br>average [min, max] (range, stddev)<br>+ 14.283kHz [9462, 19098] (9636, 4777.044922)<br>overruns: 0<br>not found: 126<br>average absolute error: -15.345 ppm<br> </div></div> </div></body>
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