[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.
Regards
Steven
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