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From: | Ralph A. Schmid, dk5ras |
Subject: | Re: [Discuss-gnuradio] cheap reference clock using a cell phone |
Date: | Sat, 6 Apr 2013 04:36:59 +0200 |
Not exactly new, but nice anyway :) I have been using the leakage of 13 MHz and its harmonics for more than a decade to calibrate other RF stuff on zero beat. It is relatively accurate, but could be better. The GSM base station usually do not have a GPS receiver here in Germany, I guess they still derive their clock from the backbone, with all inaccuracies such a system brings. Atomic clocks (rubidium systems) are down in the two digit US$ range when buying a used one, they do a fine job and need nothing more but a power supply. I installed one into my old spectrum analyzer, this solves everything when a frequency is in question, and from that I calibrated the 52 and 64 MHz clocks for my USRP. More than sufficient :) Ralph. From: address@hidden [mailto:address@hidden On Behalf Of Juha Vierinen I found something interesting on the internet today, while browsing for rtl_sdr related information. It seems like a guy called steve-m has fed his rtl_sdr dongle a clock from his mobile phone. Here is a picture: http://steve-m.de/pictures/rtlsdr_external_clock.jpg Now mobile phone networks can be used to estimate the frequency error of your oscillator, because base stations will have clocks that are in sync to a global reference. I think this is what steve-m is aiming for. Has anyone else attempted to do this? I'd be interested to hear about your experiences. It would be neat if a $8 dongle and a $20 cell phone could be combined to create a SDR locked to a global reference. juha |
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