Hi David & Simon,
To start with, rather than using two back-back radios (presumably with a
large attenuation factor in the RF connection between the two), you
could use an HF channel simulator such as;
GNU Radio https://wiki.gnuradio.org/index.php/Channel_Model
<https://wiki.gnuradio.org/index.php/Channel_Model>
Ionos (Winlink) https://winlink.org/content/ionos_simulator
<https://winlink.org/content/ionos_simulator>
PathSim http://www.moetronix.com/ae4jy/pathsim.htm
<http://www.moetronix.com/ae4jy/pathsim.htm>
(CCIR has published standardised HF channel models (eg CCIR poor) with
which to configure your channel simulator)
Once you are ready to try out your modem "over the air", to start with,
you probably only need to set up a transmitter at your QTH as you are
blessed with access to a large number of public web SDRs around
continental Europe: http://rx.linkfanel.net/ <http://rx.linkfanel.net/>
Notably, there are nearby receivers in Karlsruhe and Stuttgart, and if
you are looking for a longer path (~450 km), the receiver at the
University of Twente, Enschede, Netherlands is a good option.
Karlsruhe http://sdr.pjs.de:8073/ <http://sdr.pjs.de:8073/>
Stuttgart http://dj9kaikiwi.ddns.net:8073/
<http://dj9kaikiwi.ddns.net:8073/>
" http://bat-server.dyndns.org:8073/
<http://bat-server.dyndns.org:8073/>
" http://dl2sba.ddns.net:8073/ <http://dl2sba.ddns.net:8073/>
University Twente http://websdr.ewi.utwente.nl:8901/
<http://websdr.ewi.utwente.nl:8901/>
PS: Some very interesting research into 2x2 MIMO for HF digital channels
has been performed recently - I can send you the papers if you are
interested.
73 ZL2WRW
Ross Whenmouth
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