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

David Lord snews at lordynet.org
Sat May 2 15:47:08 UTC 2009

David J Taylor wrote:
> David Lord wrote:
> []
>> cheers
>> Both those were listed on garmin site as uk suppliers but the RS price
>> that came up was almost 170 quid and I couldn't locate the GPS-18x LVC
>> on the gpsw site.
>> I'll check both again anyway in case my eyesight was playing up.
> GPS Warehouse have them in stock.

Same as before I searched on different variations

  Results for: gps-18x lvc

Sorry no products were found for gps-18x lvc

garmin + 18x just hit the jackpot

Now ordered, thanks


> With the GPS 18 LVC, even with Windows in a non-temperature-controlled 
> environment, I'm seeing about +/- 200us (and more plus than minus, it 
> seems that each time the heating switches on it generates a positive 
> offset spike, but the thermal stabilisation takes much longer and 
> generates a more extended negative period).

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.

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.

>  http://www.satsignal.eu/mrtg/feenix_ntp_2.html
> With FreeBSD on a very old 133MHz Pentium PC, I would easily get within 
> 20us.

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


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