I'm running ntpd 4.2.7p475 on a server in my home LAN, with refclock_acts.c
patched to open the serial line at 1200 instead of 19,200 bits/second (see my
earlier e-mail "Re: Adjust serial device speed in ACTS refclock driver?").
The modem refclock, syncing to NIST, appears to be about 200 msec off with
respect to a GPS refclock which has been running for a long time on another
server in my home LAN.
Here is the output of "ntpq -c 'hostnames no' -c peers" on the server with the
modem:
remote refid st t when poll reach delay offset jitter
==============================================================================
127.127.18.0 .NIST. 3 l 83 512 1 0.000 -204.85 0.000
*10.0.229.163 10.0.229.2 2 s 27 32 17 0.169 -0.056 0.036
+10.0.229.2 .GPS. 1 s 10 32 17 0.119 0.056 0.024
10.0.229.117 10.0.229.2 2 s 60 64 3 22.133 0.553 0.116
Here are the relevant refclock configuration lines from the "ntp.conf" file:
server 127.127.18.0 minpoll 9 maxpoll 16
fudge 127.127.18.0 stratum 3 time1 0.021 flag1 1 flag2 1
(I fudged the stratum to 3 in order not to risk having the modem refclock take
over my home LAN while I'm still experimenting with it.)
And here is the last line from the "clockstats" file:
56936 8840.501 127.127.18.0 56936 14-10-06 02:27:19 28 0 -.4 021.3 UTC(NIST) *
In case it matters, I'm using a TrendNet TFM-561U USB modem.
Any ideas why the modem refclock is so far off? Is there anything I can do
about it?
Rich Wales
ri...@richw.org
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