[Moon-net] Time syncronization on JT65

[Leif Asbrink]

Hi Cris,

> Let me put in another way. If a hamradio from Mars will intend to work
> randomly with a hamradio from the earth using JT65 than they couldn't
> because they will not have the same clock standard as a reference except
> if they use an atomic clock. GPS is not working...
This may be true for the present wsjt program, but it is in no way
necessary. On a waterfall that is properly set-up one can easily 
see the transmit periods to within less than 10 seconds and
it is trivial to use that information to send the received
signal to wsjt at the right time using that information. I actually
tried it using Linrad on wideband recordings of marginal wsjt
signals. Surely the second computer running wsjt is totally unaware
of the time associated with the recording. It has to rely on my
pausing the signal until the time will become right and I can do 
that based on what I see in the waterfall display.

> So, I think this is the only reason JT65 could be considered as a
> non-random mode at all. The "chat" connection of this mode is TIME! The
> Einstein's 4th dimention. You can search in frequency but you cannot do
> the same in time. On CW, both time and frequency are random! Please
> correct me if I'm wrong.
We can indeed search in both frequency and time simultaneously. 
Of course there is a limit, with a bandwidth of 5 Hz we can not
do better than about 0.2 seconds for a signal that is just above
the average noise (in 5 Hz) With signals that QSB well below the 
noise, the time accuracy drops, but not to the extent that the
wsjt program fails. Surely it would be possible to change wsjt 
to allow a time search window of a full minute. Imagine you
have a very fast computer so you can run 15 issues of wsjt
simultaneously with a time shift of 4 seconds between each one.
(or use 15 computers)

You are wrong, but I do prefer CW myself although my reasons for
that are totally unrelated to the issues recently discussed 
on moon-net. With good tools the difference between CW and JT65 
is not too big - and a good PA can compensate for not so good
tools for CW reception at the other end;-)

Let me put it this way: I am an old man and I love CW for
no good reason....

73

Leif / SM5BSZ