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Hell on FO-20 a success



Greetings all

While experimenting with the different Hellshcreiber modes via FO-20, I was
surprised to hear another Hell signal on the satellte!  Mark, KB3CWS and I
had a short exchange just before the bird went LOS.  We agreed on a sked and
the next day worked the bird twice with the standard Feld Hell mode.  The
Hell Print from Marks signal was exelent.   Sending a series of RYRY before
each exchange helps the receiving station tune the Hell signal and adjust
for doppler.   This method works well and I didn't loose a letter through
out the entire QSO.  The large waterfall display in Nino's Hellschreiber
software http://space.tin.it/computer/aporcino/Hell/index.htm
makes it easy to spot the signal and tune it in.

Doppler shift can be a big problem with digital modes that require a high
degree of tuning accuracy, but the Feld Hell mode is very forgiving.  With a
little practice, keyboard to keyboard QSO's via satellite are easy to
accomplish with Hell.  Unlike RTTY or other digital modes the duty cycle of
Feld Hell is is about 25% which is good news for the satellites power
budget.

There is no modem involved with Hell, it works with your computers soundcard
sending the on-off tones (like CW) that produce the characters at the
receiving station similar to Fax or SSTV but without the high duty cycle.
The received tones are then "painted" onto the receiving stations computer
screen.  The weak signal advantage is obvious because of the soundcard DSP.
For more information on Hellschreiber and other "Fuzzy" modes try ZL1BPU's
site at: http://www.qsl.net/zl1bpu/

If anyone would like to see a screenshot of the Hell QSO via FO-20 please
send e-mail direct.

73, Tony
AB2CJ



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