[ntp:questions] Best practices for local clock only setup

Andreas Heinlein aheinlein at gmx.com
Mon Aug 27 13:51:46 UTC 2018


I'd like to ask you for advice on setting up a NTP server on an isolated
(i.e. air-gapped) network with a locally connected USB clock (Gude USB
mouseClock II) as the only reference.

I have managed to get this set up, but obviously reception of the DCF
signal is sometimes bad. We find "parse: convert_rawdcf: INCOMPLETE DATA
- time code only has x bits" in syslog, and the output of 'ntpq -c cv -c
rv' shows it is in state "bad format" every now and then. I failed to
find a place on our site where this does not happen, and I already
bought a second clock to rule out bad hardware.

This alone probably wasn't a problem, but we also noticed ntpd dies
every few days without any traces in the syslog. This morning, systemctl
showed me that ntpd had exited on morning of 08/26, and the last log
line was one of these "INCOMPLETE DATA" lines. No hint what caused it to
exit. I guess this is related to the reception problem.

Does anyone have experience with such a setup? There is a version of the
mouseClock with a BNC connector for an external antenna, but it is quite
expensive (~190€/$200), could this help? What antenna would we need?
I already took a look at USB GPS receivers, but these too are quite rare
these days and not cheap either.


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