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" <[email protected]>
To: "Discussion of precise time and frequency measurement"
<[email protected]>
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 <[email protected]> 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
<[email protected]> 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 -- [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.
_______________________________________________
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.
