[pskmail] Re: The hardware modem idea (sri, long rant)

  • From: John Douyere <vk2eta@xxxxxxxxx>
  • To: pskmail@xxxxxxxxxxxxx
  • Date: Tue, 1 May 2012 23:55:44 +1000

Hi Demetre,

Thank you for taking the time to explain your views.

Hihi regarding the hint. Thank you for your comments. On this subject I
would say two things, first that I personally like the concept of open
source systems and software and wish to continue supporting it, and two in
any case I am really really short of time to do any justice to another
development.

Regarding the portable situation, what you describe really represents what
I use: the FT817 and Android phone plus a 6000mAh lithium-ion battery to
power the FT-817 and recharge the phone through a 12 to 5V adapter. Plus a
small foldable solar panel in case of longer than expected circumstances.

Regarding the speed hopefully we will get there in time. I have worked on
faster modes not because of personal needs but because of requests from
other users as I am not convinced that in real life it is that critical.

Although we all like to drive/dream of driving a (red) sport car for fun,
most of us don't use one for going to work. So I personally feel that there
is a bit of the Ferrari syndrome in there. Nothing wrong with that, just
that it may be more of a "want" than a "need" in marketing terms.

On the other hand yes  robustness as you mentioned in your previous email
is important  ("at decent speed" I would add, whatever that means in
numerical terms). As Per explained I think we can claim very good
robustness at present BUT at the (somewhat dramatic) price of speed.

With modes like THOR4 we now get down to about -18dBs of s/n in less than
200Hz B/W, but boy it is slow and is a drain on batteries of portable
operations but for the simplest of transmissions.

The new modes are also targeted at filling these gaps both in the middle
and the top speed bracket, and hopefully in the future I will find the time
(or another developer will join us) to implement the Turbo codes which will
bring us closer to the Shannon limit, thereby increasing speed for the same
s/n ratios.

Again thank you for your input on the +/- of Pskmail.

73, John


On Tue, May 1, 2012 at 10:40 PM, Demetre SV1UY <demetre.sv1uy@xxxxxxxxx>wrote:

> On Tue, May 1, 2012 at 1:44 PM, Per Crusefalk <per@xxxxxxxxxxxx> wrote:
> > Hi Demetre,
> >
> > Thanks for the input, this is of course an interesting subject.
> >
> > If we were going to develop a synchronous protocol with very tight
> > timing requirements, like pactor, then the real time requirements would
> > be correct. But, we are not doing that, asynchronous ARQ modes don't
> > have any problem with reasonable speed switching time.
> >
> > Also, I think some of the modes being used now are very robust. A few
> > weeks ago I was away skiing and I brought my FT-817 and a fishing rod.
> > The antenna I made was too short and I forgot my radials at home (only
> > had one real radial). At times I could hear the servers anyway and I was
> > able to send my position and a few short emails using only 3 watts and
> > Thor modes. I can't imagine how bad my signal must have been but it
> > worked.
> >
> > Btw my portable soundcard interface is a small home made thing that is
> > attached to the cables between the radio and the pc (no extra box
> > there).
> >
> > Regarding the QRM and finding a clear frequency I am really glad that we
> > stay within 500 Hz all the time. Other systems can sometimes decide to
> > increase from 500 Hz to 1600 or 2400 Hz in the middle of traffic
> > exchange and that has caused some QRM. If we decide to use wider modes
> > later I hope we can agree to try to avoid that issue. I like to stay
> > narrow (filtered) when QRP portable so I will support strict 500 Hz
> > channels. The hidden transmitter problem is helped in part with the
> > european servers talking to each other through the big ear server. When
> > my server transmits on 10148 it notifies the others and they wait, even
> > if they can't hear the actual transmission.
> >
> > So, no, I still don't think we need a hardware modem.
> >
> > 73 de Per, sm0rwo
>
> FB FB FB Per,
>
> No worries OM. I just thought it is a bit weird doing ARQ with
> asynchronous modes, but of course this is my opinion from the
> experiences I've had until today. If it works fine for you and you are
> happy with it, all is FB.
>
> I have tried PSKmail many times, but it really is extremely slow when
> I compare it with WINMOR or my PTC-II and P4dragon. Pactor 2 can work
> in a 500 HZ wide bandwidth and you can benefit from it's filtering and
> it is at least 4 times faster than PSK500 and very ROBUST.
>
> Of course I could justify such a slow speed when operating portable
> especially with andPSKmail client and an FT-817 in your backpack,
> because carrying even an eeePC701 in a backpack and taking it up the
> mountain can be a burden, for me nowadays anyway. This setup is really
> portable and nothing can ever beat that for simplicity and lightweight
> ability. So congrats go to VK2ETA for this.
>
> I only wish John VK2ETA could write an Android client for WINLINK2000
> using a PTC-II modem or WINMOR, hint hint John, hi hi hi!!!
>
> In any case you are all doing a great work and I look forward to
> future releases when the freezes go away!
>
> Good luck.
>
> --
> 73 de SV1UY
> Demetre Ch. Valaris
> e-mail: demetre.sv1uy@xxxxxxxxx
> Radio e-mail: sv1uy@xxxxxxxxxxx
> http://www.qsl.net/sv1uy
>
>

Other related posts:

  1. Home
  2. pskmail
  3. Archive
  4. 05-2012