This is merely a historical archive of years 2008-2021, before the migration to mailman3.
A maintained and still updated list archive can be found at https://lists.osmocom.org/hyperkitty/list/osmocom-sdr@lists.osmocom.org/.
Ralph A. Schmid, dk5ras ralph at schmid.xxxI am sure, a BCCH is a BCCH, this does not hop at all, and the frequency hopping carriers do not hop some KHz, but in a sequence over a fixed scheme of normal ARFCNs. There is no free frequency choice in GSM, hopping or not. Ralph. From: Nikos Balkanas [mailto:nikos.balkanas at eyeonix.com] Sent: Friday, January 31, 2014 12:01 PM To: Ralph A. Schmid, dk5ras Cc: Richard Koch; osmocom-sdr at lists.osmocom.org Subject: Re: kalibrate-rtl results... On Fri, Jan 31, 2014 at 12:47 PM, Ralph A. Schmid, dk5ras <ralph at schmid.xxx> wrote: 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. Are you sure about that? Check it out: https://svn.berlin.ccc.de/projects/airprobe/wiki/A Legend of first picture. If still in doubt that *most" GSM carriers are hoppers, use rtl_power to scan your region ;-) Nikos Ralph. From: osmocom-sdr-bounces at lists.osmocom.org [mailto:osmocom-sdr-bounces at lists.osmocom.org] On Behalf Of Nikos Balkanas Sent: Thursday, January 30, 2014 7:35 PM To: Richard Koch Cc: osmocom-sdr at lists.osmocom.org Subject: Re: kalibrate-rtl results... On Thu, Jan 30, 2014 at 8:21 PM, Richard Koch <n1gp at hotmail.com> wrote: I'm attempting to calibrate my RTL dongles. I notice they are all about 2-4khz off if I compare against a known broadcast station's frequency. I am trying out kalibrate-rtl and am getting varied results. I am in the US, so I did a 'kal -s EGSM -g 20' and got the following: chan: 991 (928.4MHz + 26.986kHz) power: 448020.99 chan: 1002 (930.6MHz - 5.631kHz) power: 320357.07 chan: 1003 (930.8MHz + 16.192kHz) power: 109489.92 Then 'kal -c CHANNELNUM -g 20' for each channel number. I then get the results below which the average frequency error looks different for each channel. It is consistent though if I run them multiple times. I would have expected less frequency error since I know that it is really only about 4Khz off. Or am I not reading the results correctly? Results seem OK. Do not forget that most BSTs hop around in their allotted 20 Khz channel. So a result of +/- 20 Khz shouldn't surprise you. Best calibrate against "anchor" BSTs that are steady. And yes, recommendation is to calibrate against 3 BSTs and correct for the average or stddev if you wish... Nikos -Rick Using device 0: Generic RTL2832U OEM Found Fitipower FC0013 tuner Exact sample rate is: 270833.002142 Hz Setting gain: 100.0 dB kal: Calculating clock frequency offset. Using E-GSM-900 channel 991 (928.4MHz) average [min, max] (range, stddev) + 21.342kHz [17837, 27433] (9596, 3402.206299) overruns: 0 not found: 199 average absolute error: -22.988 ppm Using device 0: Generic RTL2832U OEM Found Fitipower FC0013 tuner Exact sample rate is: 270833.002142 Hz Setting gain: 100.0 dB kal: Calculating clock frequency offset. Using E-GSM-900 channel 1002 (930.6MHz) average [min, max] (range, stddev) - 11.529kHz [-15293, -5679] (9614, 3640.780273) overruns: 0 not found: 194 average absolute error: 12.389 ppm Using device 0: Generic RTL2832U OEM Found Fitipower FC0013 tuner Exact sample rate is: 270833.002142 Hz Setting gain: 100.0 dB kal: Calculating clock frequency offset. Using E-GSM-900 channel 1003 (930.8MHz) average [min, max] (range, stddev) + 14.283kHz [9462, 19098] (9636, 4777.044922) overruns: 0 not found: 126 average absolute error: -15.345 ppm -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.osmocom.org/pipermail/osmocom-sdr/attachments/20140131/1e0f9a1b/attachment.htm>