OK thanks for the pointer to joe taylor will look him up. This would be familiar to the very weak signal work I was doing years ago about 15 and I used discreet ICs to process very weak signals that were slow. But we would use a common view reference such as wwvb or a am radio station. These days you would do it all in a sound card. Regards Paul.
On Wed, Nov 7, 2012 at 6:53 PM, Alan Melia <alan.me...@btinternet.com>wrote: > Hi Paul think synchronous data transmission where you cant detect enough > signal to synchronise reliably via the bit edges received. Initially > developed for LF (136kHz) where the ERP of amateur antennas is very low. > Google Joe Taylor but not for his Nobel prize, who's original interest was > Moonbounce communication. He has now generated modes for LF too. > Alan > G3NYK > > ----- Original Message ----- From: "paul swed" <paulsw...@gmail.com> > To: "Discussion of precise time and frequency measurement" < > time-nuts@febo.com> > Sent: Wednesday, November 07, 2012 10:11 PM > Subject: Re: [time-nuts] Is it sensible to update every few seconds from > NTPserver? > > > > Interesting I am unaware of any amateur service requiring that tight of >> a timing relationship. >> At least modern PC clocks do not drift that badly in a few minutes. So it >> is pretty odd. >> Without further detail I am at a loss for why you need to do that. >> Maybe he is tinkering with spreadspectrum? >> Regards >> Paul >> >> On Wed, Nov 7, 2012 at 5:04 PM, David <davidwh...@gmail.com> wrote: >> >> Some Windows NTP clients like Tardis can calculate and implement a >>> clock frequency adjustment instead of stepping the clock if the time >>> adjustment is below a specified limit. If he was using an application >>> that was upset by the time being stepped, then that might allow less >>> frequent updates. >>> >>> If he is polling that often to maintain accurate time, then I would >>> assume he is using a local known to be accurate NTP server. >>> >>> There are Windows NTP clients which will synchronize to GPS PPS time. >>> That should be better than stock hardware and Windows can handle >>> anyway. Something like a Garmin GPS18 is specified to be within 1uS >>> and has a pulse to pulse jitter in the 10s of nanoseconds. >>> >>> On Wed, 7 Nov 2012 21:41:36 +0000, David Kirkby >>> <david.kir...@onetel.net> wrote: >>> >>> >Someone at my radio club uses some mode of operation where accurate >>> >time is required. He said the standard Windoze clock does not keep >>> >sufficiently accurate, so he has software which updates from an NTP >>> >server every 4 seconds or so. It's not exactly a denial of service >>> >(DOS) attack, but seems almost close to it in NTP terms to me. I can't >>> >really believe updating every few seconds is sensible myself, but he >>> >assures me it works very well. (I'm rather hoping it does not use a >>> >stratum 1 server!) >>> > >>> >I'm sure someone will say if you want accurate time on a PC, to use >>> >some combination of GPS, rubidium or OCXO with a 1 pps pulse and a >>> >serial port on a FreeBSD or similar computer. But that's probably not >>> >practical if your software only works on Windoze. >>> > >>> >Any comments? >>> > >>> >Dave, G8WRB. >>> > >>> >_____________________________**__________________ >>> >time-nuts mailing list -- time-nuts@febo.com >>> >To unsubscribe, go to >>> https://www.febo.com/cgi-bin/**mailman/listinfo/time-nuts<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<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<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<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.