At 11:28 10/01/2003 -0500, you wrote:
Dear Jim and group,
no criticism intended, but in my opinion machine-decoded modes like Jason
or WOLF have one disadvantage for long-haul propagation experiments: They
are exclusive, in the sense that potential receivers on the far side can
only see one signal at a time, whereas visual modes like QRSS or DFCW
allow several stations transmitting side by side.
73 es best of luck
Markus, DF6NM
Dear Markus, LF group,
This is certainly a drawback of current digital modes - but not necessarily
so with a "slow" mode like Jason, where the operator can read the received
information at a much faster rate than the data is transmitted. In
principle at least , you could do this: Digitise a relatively large
bandwidth as a .wav file or similar, and store , for the sake of argument,
30 minutes worth of data in memory. Then generate a waterfall display from
this data , so that the operator could see the signals present. Then the
operator could specify the frequency of a signal of interest, and the
demodulation/ decoding DSP algorithm could decode the signal, again using
the same data in memory. Having done that, the operator could repeat the
procedure with another signal, and so on. Since Jason et al transmit data
slowly, and DSP algorithms can run quite fast, it should be possible to
receive, store and process several signals simultaneously, and display them
sequentially.
Maybe that is a job for some future piece of software - but if you have a
few PCs lying around in the shack, there is nothing to stop you doing it
now - connect them all to the RX audio output , set one up with a waterfall
display to identify signals of interest, then set up the rest running Jason
decoders (or other modes, for that matter), so that as soon as a signal is
identified, one of the other PCs can be assigned to decode that signal .
At the moment, since there is no more than 1 Jason signal most of the time,
this would only require 2 PCs, one to monitor the Jason frequency, and one
to monitor the QRSS frequencies. The problem would be that the RX bandwidth
would have to be wide enough to include 135.9xx kHz, as well as 137.5kHz.,
so the RX would probably be overloaded if anyone local was QRV in the CW
band segment . But that might not be a problem in the USA. An easy solution
would be If I transmitted the Jason beacon closer to the "transatlantic"
segment, so that all the signals would fit through a CW filter. If anyone
would care to try this, and would care to nominate a suitable frequency
near 135.9kHz, I could do that now.....
Cheers, Jim Moritz
73 de M0BMU
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