[pskmail] Re: 300 Baud Rate in the USA

  • From: David Kleber <kb3fxi@xxxxxxxxx>
  • To: "pskmail@xxxxxxxxxxxxx" <pskmail@xxxxxxxxxxxxx>
  • Date: Tue, 7 Feb 2012 00:04:32 -0800 (PST)

I took part in testing of off the shelf amateur gear back around 2007 with a 
simple audio tone generator, and from what I recall, we found a pretty 
consistent and reliable audio response on FM audio band pass of about 4.5kh 
with pretty sharp drops at the edges. I think a 3.5 - 4k width would be well 
within the reasonable limits of most transceivers and repeaters.

I'm very interested in the results of your testing and would be glad to help 
with any testing. I'd love to Software Jockey some of your experimental modes!

-Dave, KB3FXI
paNBEMS.org



________________________________
 From: John Douyere <vk2eta@xxxxxxxxx>
To: pskmail@xxxxxxxxxxxxx 
Sent: Tuesday, February 7, 2012 2:51 AM
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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