[pskmail] Re: vhf/uhf relays

  • From: vk2eta@xxxxxxxxx
  • To: pskmail@xxxxxxxxxxxxx
  • Date: Wed, 30 Jun 2010 06:09:18 +0000

Hi Steven,

Yes that mode list has been in the back of my mind for a while. A little background first:

The current list was made for HF only and it has two variants: one limited to baud rates below 300bauds (for NA and the FCC rule) and therefore up to psk250/250R speed, and one above with modes up to psk500.

The client can connect to the server in any mode that supports the character set required by pskmail (it must include control characters), but the server may not automatically change speed from that mode.

Also, the server can listen in any mode which is in Fldigi and has the proper character set like MFSK64 for example.

So in the current state of the application, if we omit the capability to auto-adjust the mode to the conditions, it is possible to use modes outside the two hard coded lists mentioned above.

In my tests, MFSK and THOR performed beautifully on VHF FM. There was virtually no difference with VHF in SSB mode in terms of sensitivity.

Now for your question proper: In the past I had envisaged for other applications (wider band, faster speed, FM etc...) to have a list of modes passed dynamically to the server to let it know that this is the list we wish to use, and what mode to use first in the next transmission. Since the client is slave both from a protocol and mode selection point of view this should be possible but would require changes in the server and client.

The only issue I have at present is "what for" and here is the dilemma I face: the current list of modes goes up to PSK500 (for us here and in EU) and that delivers around 800 words per minute (at an average of 6 characters as per Fldigi definition) while fitting the signal in a 500Hz CW filter.

When I compare the wider modes like MFSK64 (1000Hz bandwidth) which delivers 240 words per minute I wonder what is the advantage. In my tests with Pskmail I have used MFSK64 several times and I have to say that the robustness is not that great (way down on MFSK32 and below which is logical).

Even if conditions are not perfect and PSK500R is needed, this still gives 440 words per minute, almost double the MFSK64 rate.

In practice on average links I find the PSK500R and PSK250R quite good. And then the MFSK/THOR modes kick in for the more difficult situations.

So I am open to suggestions as to the objective and application regarding the list of modes.

Please note that this list is the result of many hours of PSkmail QSOs and we did cull a number of modes that were not adding value based on on-air tests.

On another subject: how did you go with the digital modes workshop last weekend?

For information, I will be in central NSW (100KM south of Cobar) next week and will be active with Pskmail. So if anyone wants to test a server's setup I would be glad to give it a go. 40 and 80M will be the bands of choice I believe (500KM strait line).

All the best,

73, John (VK2ETA)

On Jun 30, 2010 2:32pm, 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.



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