Hi Jim, Did you look at the below article? http://www.rtl-sdr.com/a-multi-channel-coherent-rtl-sdr-product-for-passive-radardirection-finding-and-more/ --     Björn Sent from my smartphone. -------- Original message --------From: jimlux <jimlux@earthlink.net> Date: 07/03/2017 22:08 (GMT+01:00) To: Discussion of precise time and frequency measurement <time-nuts@febo.com> Subject: [time-nuts] time/sampling behavior of RTL-SDR Has anyone ever looked at the timing consistency/behavior of the cheap RTL-SDR dongles? That is, if you feed a sine wave in and get the samples out via the USB interface, are there missing samples?  What's the ADC clock look like? If you had two of them, and you determine the relative phase of them at some time t0, and you let it run for minutes, how far will it have moved? _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.

On 3/7/17 3:50 PM, bg wrote: > Hi Jim, > Did you look at the below article? > http://www.rtl-sdr.com/a-multi-channel-coherent-rtl-sdr-product-for-passive-radardirection-finding-and-more/ > -- Björn hadn't seen that one, but in my application the RTLSDRs are separated by substantial distances, so feeding a coherent reference isn't practical. However, the bistatic radar is fascinating. Juha Vierinen also has a nice bistatic ionosonde program for a USRP. I've always wanted to build a radio camera using cast-off Ku-band DBS dishes/LNBs, and the block of RTLs would work nicely for that. > Sent from my smartphone. > -------- Original message --------From: jimlux <jimlux@earthlink.net> Date: 07/03/2017 22:08 (GMT+01:00) To: Discussion of precise time and frequency measurement <time-nuts@febo.com> Subject: [time-nuts] time/sampling behavior of RTL-SDR > Has anyone ever looked at the timing consistency/behavior of the cheap > RTL-SDR dongles? > > That is, if you feed a sine wave in and get the samples out via the USB > interface, are there missing samples? What's the ADC clock look like? > > If you had two of them, and you determine the relative phase of them at > some time t0, and you let it run for minutes, how far will it have moved? > > > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. >

On 3/7/17 9:29 PM, jimlux wrote: >> Sent from my smartphone. >> -------- Original message --------From: jimlux <jimlux@earthlink.net> >> Date: 07/03/2017 22:08 (GMT+01:00) To: Discussion of precise time >> and frequency measurement <time-nuts@febo.com> Subject: [time-nuts] >> time/sampling behavior of RTL-SDR >> Has anyone ever looked at the timing consistency/behavior of the cheap >> RTL-SDR dongles? >> >> That is, if you feed a sine wave in and get the samples out via the USB >> interface, are there missing samples? What's the ADC clock look like? >> >> If you had two of them, and you determine the relative phase of them at >> some time t0, and you let it run for minutes, how far will it have moved? > Aha, someone has measured the Allan Deviation (although they don't say how) http://www.rtl-sdr.com/wp-content/uploads/2015/03/rtl_R820T2.pdf

The Allan deviation is not frequency stability - it's the ADEV of the noise on the receiver signal. Cheers Michael On Thu, 9 Mar 2017 at 3:00 am, jimlux <jimlux@earthlink.net> wrote: > On 3/7/17 9:29 PM, jimlux wrote: > > >> Sent from my smartphone. > >> -------- Original message --------From: jimlux <jimlux@earthlink.net> > >> Date: 07/03/2017 22:08 (GMT+01:00) To: Discussion of precise time > >> and frequency measurement <time-nuts@febo.com> Subject: [time-nuts] > >> time/sampling behavior of RTL-SDR > >> Has anyone ever looked at the timing consistency/behavior of the cheap > >> RTL-SDR dongles? > >> > >> That is, if you feed a sine wave in and get the samples out via the USB > >> interface, are there missing samples? What's the ADC clock look like? > >> > >> If you had two of them, and you determine the relative phase of them at > >> some time t0, and you let it run for minutes, how far will it have > moved? > > > > > Aha, someone has measured the Allan Deviation (although they don't say how) > > http://www.rtl-sdr.com/wp-content/uploads/2015/03/rtl_R820T2.pdf > > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. >

On 3/8/17 1:14 PM, Michael Wouters wrote: > The Allan deviation is not frequency stability - it's the ADEV of the noise > on the receiver signal. In that article, I think the idea was that they fed a very stable tone in, and so they're essentially measuring the ADEV of the LO. He unfortunately didn't say what the signal he was feeding in was, though. Or was he just integrating the white noise out of the box? Well, I should get some of these tonight, and if all goes well, and there's no panic at work, maybe I can hook one up and look at the 100 MHz maser signal downstairs. > > Cheers > Michael > > On Thu, 9 Mar 2017 at 3:00 am, jimlux <jimlux@earthlink.net> wrote: > >> On 3/7/17 9:29 PM, jimlux wrote: >> >>>> Sent from my smartphone. >>>> -------- Original message --------From: jimlux <jimlux@earthlink.net> >>>> Date: 07/03/2017 22:08 (GMT+01:00) To: Discussion of precise time >>>> and frequency measurement <time-nuts@febo.com> Subject: [time-nuts] >>>> time/sampling behavior of RTL-SDR >>>> Has anyone ever looked at the timing consistency/behavior of the cheap >>>> RTL-SDR dongles? >>>> >>>> That is, if you feed a sine wave in and get the samples out via the USB >>>> interface, are there missing samples? What's the ADC clock look like? >>>> >>>> If you had two of them, and you determine the relative phase of them at >>>> some time t0, and you let it run for minutes, how far will it have >> moved? >>> >> >> >> Aha, someone has measured the Allan Deviation (although they don't say how) >> >> http://www.rtl-sdr.com/wp-content/uploads/2015/03/rtl_R820T2.pdf >> >> >> _______________________________________________ >> time-nuts mailing list -- time-nuts@febo.com >> To unsubscribe, go to >> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. >> > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. >