[time-nuts] Is it sensible to update every few seconds from NTP server?

David davidwhess at gmail.com
Thu Nov 8 02:34:43 UTC 2012


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, shalimr9 at gmail.com 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 <david.kirkby at onetel.net>
>To: Discussion of precise time and frequency measurement <time-nuts at febo.com>
>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,  <bjones0 at mindspring.com> 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
>
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