The symbol time for JT65 is 2.69 baud or 0.372 seconds so one symbol is about 70,000 miles of propagation. The information I found online says synchronization needs to be within 1 or 2 seconds for decoding and closer is better.
http://www.qsl.net/zs2pe/VHF/Downloads/JT65%20Technical%20Specs.txt If the OS clock was screwed up because of the issues I mentioned earlier, synchronizing every few seconds might be needed to make it work. I sure would try fiddling with CPU power management though to fix it. On Wed, 7 Nov 2012 19:42:38 -0600, [email protected] wrote: >That sounds odd, as most radios take tens of millisecond, if not hundreds to >switch from transmit to receive and back in any mode other than break-in CW. > >Further JT65 is used with propagation modes that typically do not have a >stable or predictable propagation time like moonbounce or meteor scatter, so I >don't understand why mS timing would be necessary? > >I must be missing something. > >Didier KO4BB > > >Didier > >Sent from my Droid Razr 4G LTE wireless tracker. > > > >-----Original Message----- >From: David Kirkby <[email protected]> >To: Discussion of precise time and frequency measurement <[email protected]> >Sent: Wed, 07 Nov 2012 5:47 PM >Subject: Re: [time-nuts] Is it sensible to update every few seconds from NTP >server? > >On 7 November 2012 23:28, <[email protected]> wrote: >> We had a presentation at our radio club several months ago on digital HF >> modes, and part of the presentation was on JT65 and apparently it needs >> a precise synchronized time fix on both ends for an exchange to occur. >> I do not recollect all of the details that were presented, but they did >> say that the default windows time keeper is not accurate enough, and >> advocated installing a third party ntp client that updates (way too) >> frequently. >> >> -Brian > >I think it might be JT65 he is using. I know he said that if your time >was accurate to 1 ms, and someone elses 2 ms, you have a higher chance >of making the QSO. Hence there is a need for accurate timing. (I'm not >sure he said those exact figures of 1 and 2 ms, but the general point >was that it needed to be accuate, and increased accuracy gave a higher >chance of making the QSO). > >But the whole idea of getting time from an internet time server every >few seconds seemed odd to me. He is not using any local time server. > >I'll try to find out what mode he is using, and what software to >correct his time. > >Dave > >_______________________________________________ >time-nuts mailing list -- [email protected] >To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >and follow the instructions there. >_______________________________________________ >time-nuts mailing list -- [email protected] >To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
