Dear Dave, Gary, Jay, LF Group,

Thanks for the comments - Yes, with a bit more work I hope to convert this
into a publishable article.

As far as achieving the "legal limit" ERP goes, the UK licence regulations
for 136k and 500k don't currently specify a TX power limit, just an ERP of
1W and 100mW respectively. How you determine the ERP isn't specified either,
although for the 500k Special Research Permit you are required to explain
how you intend to achieve compliance. So in principle you can just turn up
the power until the limit is achieved. This is easily done on 500kHz (about
9W needed for the home QTH antenna, against 1.5W for the open field antenna
to get 100mW ERP), but not really feasible on 136k, which would need only a
few hundred watts for 1W ERP with the open field antenna, but 4 - 5 kW for
the home QTH antenna, which would probably suffer breakdown of some form
before this level was reached.

Cheers, Jim Moritz
73 de M0BMU