Re: [Discuss-gnuradio] cheap reference clock using a cell phone

[Ralph A. Schmid, dk5ras]

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
Sent: Friday, 05 April, 2013 21:13
To: gnuradio mailing list
Subject: [Discuss-gnuradio] cheap reference clock using a cell phone

 

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