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Hellshcreiber on OSCAR 10



Greetings all...

By now many of us are familiar with PSK31 and it's outstanding weak signal
capability. It's really amazing what this mode can do when working HF dx ,
especially when narrow filtering is applied.   However, it's nearly
impossible to utilize this mode with satellites because of doppler shift and
the precise tunning requirement needed for this mode.

The Hellschreiber mode has nearly the same weak signal capability and is
much less sensitive to doppler tunning.  I was surprised at how well this
mode works with the large amount of doppler shift that FO-29's 70cm downlink
offers.  Although automated doppler tunning would make things easier, it's
not difficult to retune for doppler by hand... one only needs to keep an eye
on the waterfall display built into most  Hellshcreiber software.

last night, I experimented with Hellshcreiber on OSCAR 10.  I used the
IZ8BLY soundcard program and recorded my downlink with an analog tape
recorder.  I then played the recorded Hellshcreiber signal back to the
soundcard with the software running.  The print was clear and easy to read
despite the QRN from the 2 meter downlink.  The sattellite was at 21,000km
and the uplink power was 30 watts. Similar experiments on RS-13, FO 20 and
29 also yeilded 100% print.

 Hellscheiber is a CW like mode in that it's part digital and part analog,
similar to facsimile.  The charactors
are in dot matrix form and appear to paint themselves accross the screen as
the Hell signal is received. The duty cycle of this mode is 21% so it dosnt
tax the satellite like SSTV , RTTY or even CW!

It  seems to me that this is one of the best keyboard modes for satellite
work in terms of low duty cycle,  and the ability to cope with doppler
shift.  For those who enjoy keyboard ops and satellite work, it's worth
looking into.  At the very least, the ease of operation and readily
available software may generate a bit more activity on the birds.

If anyone would like a screen shot of the test results, please e-mail
direct.

73, Tony/AB2CJ

IZ8BLY soundcard program -
http://www.freeweb.org/varie/ninopo/iz8bly/Hell/index.htm
ZL1BPU's Hellshcreiber page - http://www.qsl.net/zl1bpu/



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