Rik. No one has suggested that experimenting on 136 khz should stop.
Your Broadcast friend was amazed that you should try 1w ERP for
communications on LF. He is not well informed. Marine Radio/Electonics
Officers on ships and shore bases have been communication worldwide on
500 khz as the norm with very low ERP's and lower down in frequency  the
Aeronautical beacons have been heard over thousands of kilometres, they
also have very low ERP's.( a few WATTS or less).When you get to 30 khz
and below that is a totally different story. What Frontiers are we about
to Cross. It has all been done before but some of us just want  to
re-invent the wheel and have some fun. Think of all the real DX that we
are missing on the other bands and all the real drama on the Satellite
and Gigahertz bands not to mention 160 Metres hi
73 de Mal/G3KEV(operational on all of these bands but spending too much
time on 136 khz )