[pskmail] Re: 300 Baud Rate in the USA
- From: "DAVID GRAY" <kf4wbs@xxxxxxxxxxx>
- To: <pskmail@xxxxxxxxxxxxx>
- Date: Tue, 7 Feb 2012 11:13:16 -0500
JOHN
WHAT ARE YOU GOING TO USE AT THE SERVER AS A MODEM ?
THE MARS GROUP CAN USE THOSE SPEEDS ON HF
BUT FLDIGI WONT RUN THAT
DAVID
From: John Douyere
Sent: Tuesday, February 07, 2012 02:51
To: pskmail@xxxxxxxxxxxxx
Subject: [pskmail] Re: 300 Baud Rate in the USA
Hello David and Pskmail operators,
Just to give you a heads up.
Following Dave's request on faster modes for VHF I had a lot of fun driving the
digital mode equivalent of a Ferrari (well, maybe just a turbo-charged Porshe
today).
I tried various combinations of multiple carriers with PSK500 / PSK500R and
PSK250 / PSK250R, up to 4 carriers and I have to say it works well.
To the point where the slower of my two PCs could not handle the speed of
characters coming in, but that can be fixed.
So far my highest test has been 4 x PSK500, using approx 2.6KHz of bandwidth
and producing speeds of around 3200 words per minute. By changing the coding to
the MFSK varicode I should be able to get around 3500 words per minute.
This can be used with Pskmail or the Flxxx series of message handling.
Of course the signal to noise of the channel has to be better and better as we
increase the bandwidth and speed but in a good FM channel it should be fine.
In my initial tests I find that an extra 8dBs of s/n ratio is required for the
PSK Robust modes using 4 carriers instead of 1 (for 4 x the speed), and 15dBs
extra required for the standard PSK modes when going from 1 to 4 carriers.
The PSK Robust modes give excellent results, with very good sensitivity but at
half the rate of the PSK modes of course.
More tests required, but impressive so far.
More of interest to the HF Pskmail operators, I have also tested with great
success a 2 carrier PSK250 and PSK250R which give the same speed as PSK500 /
500R respectively and use 600Hz of bandwidth. Since these are at only 250 baud
they are allowed in the USA on HF. Are there other restrictions on the HF bands
like bandwidth in North America?
Also, I searched through the internet but I could not find references in regard
to the actual audio bandwidth of Amateur transceivers in FM. Has anyone got
some references in that regards?
All the best,
73, John
On Sat, Jan 28, 2012 at 2:45 AM, David Kleber <kb3fxi@xxxxxxxxx> wrote:
Good point, Victor.
I more likely scenario would be a major cyber attack that would have equally
damaging results. And, of course, on the local level, any situation that has
everyone trying to use the cellular system at the same time will result in
service outages (same thing goes with public safety trunked radio systems).
For emcomm on HF, I see amateur radio being useful for situational awareness
bulletins, the movement of bulk messages and logistical data. But, I see much
more value that we could add at the local level (which is where the action is).
MT63 2k long FEC/nonARQ is serving us very well but we're only using 2k of the
4.5k usable audio spectrum that is typical of most traditional FM transceivers
and repeaters. A 3-3.5K mode would fit nicely. I like the nonARQ for our
manned station ops and MT63 2k long is quite reliable, even on long
transmissions. FLWRAP and FLMSG allows all the receiving stations to confirm
100% and MT63 2k long is very tolerant to poor conditions and will even
tolerate up to almost a full second of lost audio without missing a beat.
That's why my wish list includes a very heavy FEC mode and would tolerate a
moderate amount of FEC delay for our purposes.
On the other hand, I'd like to see a new 3.5k high speed mode with just a
little FEC for ARQ with a local pskmail server for emcomm use. I think this
could be of great value for local emergency communications.
-Dave, KB3FXI
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