LF techniques covering every aspect have been documented over the years
and while some purport to be inventing new methods they are really
copying what has gone before. The broadcast industry has covered it in
great depth and the various Government Agencies have also perfected the
two way communications aspect especially narrow band methods. It seems
the majority interested in LF do not realise this and think they are a
first. Government agencies have used LITTLE and LARGE antennas, high
power and low power and know all the answers, a lot of which is in the
public domain. It is rumoured that fixed stations on 16 khz were
communicationg with submarines under water, at a range of 3700 miles
before most of us were born, and some amateurs are struggling to work a
few hundred miles into continental europe on 73 and 136 khz.
With the advent of 73 and 136 khz to radio amateurs  it has enabled them
to experiment on an individual basis but do not get frustrated with
mathematics and formulae and worried how to go about it, just go to the
library get the information, then go home and build it and put up the
largest VERTICAL ANTENNA that you can get into your garden. You might
then be able to work into the USA or Canada. It is not necessary these
days especially with material available on Internet to RE-INVENT the
proverbial wheel.
de G3KEV