Professional and Broadcast Engineers already know that 73 khz has a
better surface wave for the same given power than 136 khz over a given
distance. The advantage of 136 khz is the potential to cover greater
distances because of the sky wave effect. This has all been documented
if anyone cares to research the information.
Why has it taken so long for Radio Amateurs in the UK to discover this
fact, given that 73 khz has been available for several years. It was
always possible to work xband to other countries  and find out but no
one has bothered until a few  weeks ago!!!!!
Given a good VERTICAL antenna at say 100 - 120 ft with 1W erp, your
signal surface wave would greatly exceed that of a 136 khz signal. Some
have discovered lately that even a short vertical or a piece of low
slung wire is alreading doing better on 73 than 136 khz.
The UK allocation of 73 khz did not attract many participants because is
was not an International allocation, a bit like the 4 metre band, it
never attracted those with the potential to really cross frontiers.
Those mostly interested are using  G5RV type antennas strapped and an
audio amplifier!!! and sending LMCW(QRSS). Some of the qso's that I have
seen xband are suspect, there are so few active that you only need a
couple of letters of the callsign and guess the rest.
How about a proper CW qso and a proper report.
73 de G3KEV