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</o:shapelayout></xml><![endif]--></head><body lang=DE link=blue vlink=purple><div class=WordSection1><p class=MsoNormal><span lang=EN-US style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>GSM does not hop around inside its channel, this is wrong, the frequency is +- some Hz accurate, at least in normal western European commercial GSM networks.<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-US style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Ralph. <o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><div style='border:none;border-left:solid blue 1.5pt;padding:0cm 0cm 0cm 4.0pt'><div><div style='border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0cm 0cm 0cm'><p class=MsoNormal><b><span lang=EN-US style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>From:</span></b><span lang=EN-US style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'> osmocom-sdr-bounces@lists.osmocom.org [mailto:osmocom-sdr-bounces@lists.osmocom.org] <b>On Behalf Of </b>Nikos Balkanas<br><b>Sen</b></span><b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>t:</span></b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'> Thursday, January 30, 2014 7:35 PM<br><b>To:</b> Richard Koch<br><b>Cc:</b> osmocom-sdr@lists.osmocom.org<br><b>Subject:</b> Re: kalibrate-rtl results...<o:p></o:p></span></p></div></div><p class=MsoNormal><o:p> </o:p></p><div><p class=MsoNormal><o:p> </o:p></p><div><p class=MsoNormal style='margin-bottom:12.0pt'><o:p> </o:p></p><div><p class=MsoNormal>On Thu, Jan 30, 2014 at 8:21 PM, Richard Koch <<a href="mailto:n1gp@hotmail.com" target="_blank">n1gp@hotmail.com</a>> wrote:<o:p></o:p></p><div><div><p class=MsoNormal style='margin-bottom:12.0pt'>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?<o:p></o:p></p></div></div><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal>Results seem OK. Do not forget that most BSTs hop around in their allotted 20 Khz channel.<o:p></o:p></p></div><div><p class=MsoNormal>So a result of +/- 20 Khz shouldn't surprise you. Best calibrate against "anchor" BSTs that are steady.<o:p></o:p></p></div><div><p class=MsoNormal style='margin-bottom:12.0pt'>And yes, recommendation is to calibrate against 3 BSTs and correct for the average or stddev if you wish...<o:p></o:p></p></div><div><p class=MsoNormal>Nikos<o:p></o:p></p></div><div><p class=MsoNormal><o:p> </o:p></p></div><blockquote style='border:none;border-left:solid #CCCCCC 1.0pt;padding:0cm 0cm 0cm 6.0pt;margin-left:4.8pt;margin-right:0cm'><div><div><p class=MsoNormal>-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<o:p></o:p></p></div></div></blockquote></div><p class=MsoNormal><o:p> </o:p></p></div></div></div></div></body></html>