Hi Freddie...I seem to remember Long ago, some info regarding 390....The biggest AM problem
is Antenna efficiency, how much power radiates, how much is wasted in Loading coils etc

The way the Forts were constructed, Huge Concrete legs, with Rebar Metal inside it...
So not easy to get to a metal ground, for Antenna to work against

I remember reading, that Counterpoise wires were used, going Downwards from the feedpoint
So as this, was well above the sea (depending on the Tide)
It would have formed a sort of short Dipole, improving the efficiency over usual unipole

Paul Rustling when involved with the IOM station, planned a layout similar as 390 had
https://paulrusling.com/IsleofMan.html

Haven't seen Paul post on here for ages.....I know your out there.. Paul ?






Rod Watts