The SCS company has developed an alternative mode to 300 baud Packet
called Robust Packet. I've been testing it in one of their Tracker
modems ($350) for some time now and it is robust. If you like Packet and
need a modem that works under adverse conditions, this is it.
Short demo here http://www.youtube.com/watch?v=ZOLk4n1ypJU The video
was recorded during a test link between myself and N9LYA on the 20 meter
band.
I'd love to see a similar mode in FLDIGI some day.
Robust Packet Specs:
Baud Rate: 200/600
Modulation: 8 tone PSK
Bandwidth: 500Hz
Tony, K2MO
On 2/11/2012 6:07 PM, Brian Lloyd wrote:
On Sat, Feb 11, 2012 at 2:46 PM, Charles Brabham <[email protected]
<mailto:[email protected]>> wrote:
To hear some people's political opinions about Packet, you would
think that it would not work at all.
Only thing is... It does work, and has worked FB on HF for
decades. Not only that, but AX25 Packet does things that most
other digital modes simply cannot do.
If you leave off the politics and just stick with observed
reality, the fact is that no other digital mode has been developed
yet to do what Packet does - but better.
Q15x25 was a nice try, but in on the air tests, regular old HF
Packet was more robust, and provided better throughput despite the
lower baud rate. We had great hopes for Q15x25, but it did not
prove to be better than 300 baud Packet.
The old urban myth about Packet being technically unusable on HF
was started in the late 80's by amateur TCPIP buffs who were
frustrated because nobody liked amateur TCPIP.
The situation hasn't changed... HF Packet is still going strong,
and the myth-makers are still frustrated because nobody
likes amateur TCPIP.
And here I thought that the old AX.25 vs. TCP/IP wars were over. I
know I moved on. I guess there are die-hards everywhere. :-)
And for what it's worth, if we compare the success of TCP/IP with the
success of any flavor of X.25, including the mis-named AX.25, well,
the jury is definitely in on that topic. :-)
But getting back to AMPR on HF, consider: that something works does
not mean that it is optimal and cannot be made better. And my comments
about both the FSK modem and the AX.25 protocol specifics are true no
matter who speaks them. Phil Karn and I did an excellent analysis of
the AX.25 shortcomings back in the 1987 or 1988 ARRL Computer
Networking Conference. We ran computer simulations and then backed
them up with real-world observations of live networks. And the
observations and conclusions haven't changed, even after 25 years.
(Wow, has it been that long?)
So, just because it works doesn't mean it can't get better. And just
because someone who likes TCP/IP says it, doesn't mean it isn't true.
Frankly, I couldn't care less about running TCP/IP over an HF link but
I do think that it is possible to craft a better protocol that will do
what AX.25 is doing, but do it better and more reliably. It would be
quite interesting to see progress in this area rather than arguments
about how adequate it is.
73 OM
--
Brian Lloyd, WB6RQN/J79BPL
3191 Western Dr.
Cameron Park, CA 95682
[email protected] <mailto:[email protected]>
+1.767.617.1365 (Dominica)
+1.916.877.5067 (USA)
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