[OZAPRS] HF Tracker beacons and Compressed frames

Tony Hunt wavetel at bigpond.com
Tue Sep 28 09:08:31 EST 2004


Its interesting and good  to note a few more HF users appearing.. Ive also
noticed that there are some using uncompressed frames.. Now there are a
few
possible reasons why this is happening but it would seem sensible to make
comment about our settings particularly on Tiny Traks..

For those running Tiny Traks on HF you can do yourselves a real favor and
change the settings to Enable the MIC-E format. Sending uncompressed
frames
seems to produce a packet of about 96 bytes. Sending MiC-E results in a
frame of 13 bytes.. Not just a good saving on channel bandwidth but an
appreciably higher chance in actually getting a valid frame to propagate
and
decode on HF especially when its noisy or when its just poor propagation
at
the time..  There are all sorts of settings on Tiny Traks particularly the
version 3 but
this one setting is probably one of the more important ones (in my
opinion)
that makes
a real difference and also makes your efforts worth while by making it
work
effectivly.

Ive messed about alot of late on HF with messaging frames which are
typically 80-90 byte frames.. Sending these and getting them to decode is
a
challenge on HF at times.. Getting the ACKs back is far easier generally
being 13-14 bytes..

So even on 2m channels this same philosopy applies.. A NMEA string I just
saw for a mobile in VK3 was 116 Bytes whereas a compressed MIC-E frame
would
convey the same general info very quickly and more reliably.

UI-View also if used in a mobile as a traking device should be set to use
Compressed frames. There are still some devices about that cant send
compressed frames like KPC3 and TNC based trackers.. While there is no
harm
in using these it begs the question why on earth not turn on compression
if
its available??

Tony Hunt VK5AH


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