[pskmail] Re: 300 Baud Rate in the USA
- From: Remi Chateauneu <remi.chateauneu@xxxxxxxxx>
- To: pskmail@xxxxxxxxxxxxx
- Date: Tue, 7 Feb 2012 16:41:41 +0000
Hi David,
What's the limitation of fldigi in this case, please ?
Thanks
Remi
On Tue, Feb 7, 2012 at 4:13 PM, DAVID GRAY <kf4wbs@xxxxxxxxxxx> wrote:
> 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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