[aprssig] HF packet (Was Re: weak signal ISS packet)
g8kbvdave at googlemail.com
Thu Jan 15 07:34:08 EST 2015
> > I won't even start on about HF packet, that's stuck in even darker
> > places than 1200bd VHF packet/APRS.
> > Dave G0WBX.
> Maybe HF isn't so bad. We have 'APRS' on PSK and MSK with
> APRS-MESSENGER, a HF 'tracker' is being worked on and the SCS Robust
> Packet Tracker TNC is yielding some awesome world wide reception
> reports. Also the DireWolf and UZ7HO systems support 300 baud HF
> packet and their bit-error-correction helps a lot.
> Bill, WA7NWP
But it's oh so s l o w ... And all too easy to swamp the "channel".
Yes, I have used and still have configured both UZ7HO's program on Windows
(works better than just about anything else.) And DireWolf on Linux, but that is
a right royal dog to get setup correctly, as you don't get any clue as to the
tuning, untill it hears something well enough to decode it. A Catch 22 situation.
Plus it has issues with PTT control. (Hint, use both lines in opostion to get
reliable TX, and more importantly a clean transition back to RX, and configure
DW to drive one line -ve for TX!)
I use this homebrew circuit for my 706 in the mobile 4x4 toy.
It works well with DW, QSSTV and Fldigi (not at the same time of course, but no
configuration changes are needed when changing use.) I have it configured for
RTS+ with DTR- = PTT active. -Nothing- else will cause that to happen.
If I could undersand the sources (they seem more convoluted than most C code)
I'd have a crack at fixing that issue, as I've done some work with Flrig for my
TS-870. But that's like comparing chalk with chese code wise...
I have successfully built DW from sources on a Pi, so maybe....
(I just downloaded the sources for DW r1.1, will take a look again.)
APRS-Messenger, I've played with, but don't have a "use" for as yet, but am well
aware of it.
SCS RPR is indeed very good, but as the detailed protocol is not public, it's
doubtfull if it's entirely legal for "Amateur" use this side of the Atlantic, not that
it stops anyone using it. (VERY popular in Germany...)
DF1CHB has been using it airborne from commercial flights (He's a Pilot AFICT)
with great success within Europe. Not sure of the legality of that, as absolutely
no airbourn HAM activity of any type is permitted in the UK, but I dont' know in
detail how that relates to the rest of the EU.
(He does often alternate between bands, and 300bd AFSK too, either way, he
puts good signals into central UK.)
It is known that RPR uses multiple PSK signals, but what the detailed coding is,
is not known. At least, after a lot of searching, I and others have failed to come
up with a detailed spec anyone could use to create an "open" tracker or anything
else that uses that codec.
If anyone knows of an accurate source of such info, several people out here
would like to know. Else, it'll have to be reverse engineered or similar.
Monitoring 300bd AFSK, I often see digi hops (sometimes multiple!) specified. I
also found that problem when trying to use YAAC with DireWolf for both HF and
VHF tracking. At the time, I couldn't see a way to have a WIDE2-1 path on VHF,
and keep that away from HF. Andrew has done a lot of work since then, so
when I get time I'll take another look at that.
That's the problem for me, as before, never enough of "the right sort of
contiguious time" is ever available, to fully get up-to-speed with this stuff..
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