[pskmail] Remedies against multipath distortion on 30 meters

  • From: "Rein Couperus" <rein@xxxxxxxxxxxx>
  • To: pskmail@xxxxxxxxxxxxx
  • Date: Sun, 3 Jun 2012 16:44:51 +0200 (CEST)

During 2 weeks of testing jpskmail_2.0.13 from a camp site on Corsica Island,
I had to define some strategies against multipath distortion. Corsica is a volcanic
island with lots of high mountains which produce extremely strong frequency
dependent QSB. Which made it impossible to use wide modes like PSK500 and PSK500R. 
Starting with PSK500R the server (OE5RTL in Austria) did a good job of degrading
the mode to PSK250R. But the PSK250R mode was a lot more robust in this situation,
and the connection went up to PSK500R again which lost a lot of time on the link
because it takes several frames to get back down....
The remedy was quite simple: Take the PSK500/PSK500R modes out of the mode list
and call the server with PSK250R. This produced a stable connection without too much
mode switching. The mode list used was now PSK250R, MFSK32, THOR22.
That solved the problem completely. After the connected session I switched
the default channel mode (PSK500R) back on, to make sure I did not ruin the channel with my beacons....

Rein PA0R

--
http://pa0r.blogspirit.com

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