[pskmail] Re: Need PSKMail for Disaster Relief Operations

  • From: Per Crusefalk <per@xxxxxxxxxxxx>
  • To: pskmail@xxxxxxxxxxxxx
  • Date: Thu, 03 May 2007 17:54:44 +0200


I have seen 706 rigs with wider filters used here, they seem to work
fine. Also there are Skanti rigs in use that have too narrow filters 
(I believe 2.8 kHz) and they seem to work pretty good anyway (displayed
SNR on Harris RF-5710 is slightly worse). But, many have rigs with
narrow filters and it would be good to handle that. Experiments are of
course always necessary (and fun).

The compression we have been testing is the one already existing in
pskmail. If you click on the download button, instead of read, to read
an email then that email will be compressed during transport and the
client will decompress it when its completely downloaded.
First there is sort of a context based huffman where it looks for words
and compresses, then its compressed agn using gzip and last but not
least made ready for transport as base64 (the process is reversed in the
client). What we have tested now is paq7 and paq8l instead of gzip and I
have added swedish words to the word_table file in .cbh and tested that
(a lot of tests...).

The paq compression is much better than gzip and we save a lot by using
it. More on that here: http://cs.fit.edu/~mmahoney/compression/

Rein tested "daily reports" examples that Walt sent us and without
compression it took 9 minutes 38 seconds to transfer (real on air
tests). With the new compression it took 3 minutes and 28 seconds,
pretty good.

73 de Per, sm0rwo

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