[ntp:questions] Can the line audio out of HF radio be used to sync ntp. Trying to get a cheap ($) radio method.

David J Taylor david-taylor at blueyonder.not-this-part.nor-this.co.uk.invalid
Sat May 2 16:31:36 UTC 2009

David Lord wrote:
> I've ntp logs going back many years and for me chrony was better
> suited to handling temperature changes but was originally used
> because of intermittent dialup connection.

Yes, having a history of expected variations due to temperature chnages, 
or perhaps even using the termperature sensors available on the PCs, might 
enable ntp to even better than it does now.

> With ntpd and maxpoll set to a low value (8) I find ntp can
> compensate ok but there is a lot of jitter and offset wanders
> more than I'd like.
> With high values of maxpoll (13) I see great stability until
> seasonal or other temperature  changes when ntp seems to lose
> the plot.
> This is no more than happens regularly anyway due to asymmetric
> latency in the adsl connection.
> I'm expecting a pps source to make a massive difference.

Yes, from milliseconds to microseconds - if you're lucky!

> I'm using NetBSD and just had  one of servers (c3-600)
> disconnected from lan for a while and moved upstairs so I
> could get a less erratic signal from gps/dcf/msf. I need
> external aerials. I'm about 100 mile from Anthorn, 600 mile
> from Frankfurt so suspect some interfering source.
> I've previously run NetBSD-1.5 on a 486dlc33, 8MB ram, and will
> try to use one of my junk 486dx6, 20MB ram, as dedicated ntp box,
> if I can get NetBSD-5 to install, otherwise will use one of the
> servers.
> David

Here in Edinburgh I have several cheap radio-clocks, and they all seem to 
sync OK.  Removing the CRT TVs (4th harmonic of timebase near 60KHz) 
probably helped.  We are less than 120km from Anthorn.  Rather than 
power-up another PC, you will probably find the performance on a shared 
server adequate - depending on your expectations, of course.  You can run 
that serial lead for some distance.

My page describing the hardware is here.  I now have two RS232 outputs 
paralleled from the GPS 18 LVC.


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