Hello, all,

I harbored some suspicion regarding the "DT" numbers as displayed by
wsjtx in WSPR mode.  Today I made some experiment, and indeed: DT
showed an offset of -0.8 s, even though the two clocks were in
perfect sync.

Details:

I set up two laptops side by side.  I saw to it their clocks are in
sync.  Both run wsjtx in WSPR mode.  I had one of them whistle and
the other receive, directly from speaker to mike, no radio link was
involved.  The receiving laptop consistently showed a DT of -0.8 s.

In one experiment, I had them switch roles.  The now-receiving
laptop showed a DT of -0.9 s.

Both laptops run Debian Jessie on AMD64.  The wsjtx used is version
1.7.0-r6192-1~ki7mt~trusty, which I installed as described at
http://wsprnet.org/drupal/node/5567 .

To sync the clocks, I used ntpd on both laptops.  Besides some other
servers, each ntpd had the other laptop also configured as one server.
So I could ask ntpd what the time difference to the other ntpd is:
Below 10 ms.

In passing: While doing the experiment, one of the wsjtx instances
froze while decoding.  The UI did no longer move, the clock stopped,
I had to kill.

Vy 73,

Andreas, DJ3EI


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