[pskmail] Re: vhf/uhf relays

  • From: John Douyere <vk2eta@xxxxxxxxx>
  • To: pskmail@xxxxxxxxxxxxx
  • Date: Wed, 30 Jun 2010 17:00:12 +1000

Hi Brett,

Please refer to my comments in your email below.

Best 73s, John

On Wed, Jun 30, 2010 at 3:27 PM,  <pskmail@xxxxxxxxx> wrote:
> On 30/Jun/2010 00:32 Steven Heimann <steven@xxxxxxxxxxx> wrote ..
>> Hi John
>> It would be nice if the modes used by PSKMail were configurable rather
>> than being hard coded in.  In cases like this where FM will be used the
>> server could limit the modes to ones useful for FM.  Also, as the
>> channel bandwidth is fixed modes wider the 500Hz could be selected which
>> could increase speed.
>> Just a thought.

I think there are two parts to your question:

A. As mentioned in my email to Steven, I struggle with the benefits on
HF, but again I may be missing something.

B. For FM applications there would be a case for a separate list of
modes, which again could be hard coded if we take the simple coding

Alternatively, as you mentioned, we could limit the current list to
the appropriate modes for that application, but in reality the system
should be quite capable of adjusting itself as it continuously
measured the signal quality both ways and makes decisions to change
modes based on this.

I haven't performed new tests using FM since we developed the
adaptative mode feature, so if you were to do some tests we would be
glad to hear back from you. With particular interest in the way the
mode adaptation works in that case.

>> Regards
>> Steven
> Greeting-
> Is there no way to tell the server to use a wider bandwidth & higher speed 
> mode?

As mentioned above and in previous email the issue I have is that
there are no higher speed mode available at present in Fldigi that we
don't already use.

For information, we tried PSK1000 but the results were not conclusive.

> I would think one could get an easy 9600 baud in a standard FM channel.

This would be an issue of mode available in Fldigi rather than Pskmail per say.

The issue that become apparent quickly when pushing the speed envelop
towards the theoretical limit is that while if is possible to have a
lab version of a protocol working at higher throughput that what we
have now, the issue is when you get in the field, the hardware
variations (PC sound card, radio, interfaces) is so large that it is
easy to end up with a system that is not reliable and therefore does
not get used or distracts from the objective.

For example getting 9600 bauds on an FM channel required very good TX
deviation accuracy and from what I have read is not a plug and play

The other example was the PSK1000 test we did.

In the current mode list we use you can have uncalibrated sound cards
(off by thousands of PPMs) with non linear interfaces and far from
linear rigs (in terms of frequency response) and still get through.

So like life, this is full of compromises. But again we are open to new ideas.

> 73
> -Brett
> wa3yre

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