John asks for details of the Tx set up here:-

This consists of a PLL synthesiser driven by a VXO which can be pulled
enough to produce 1-2 cycles frequency shift by a small capacitor and relay.
This feeds a Decca transmitter producing about 1000W. This is transformer
coupled to a  loading coil and variometer with a max inductance of
6.5mH.which resonates the Ant. The Ant is an inv L with a vert. section 50ft
high and 600ft of top load (not in a straight line) This is all hung up in
trees which tend to absorb about half the power,so the 1000W from the Decca
produces about 400mW at the Ant. and about 200mW is radiated.
I use QRS by Rik Strobbe to produce the DFCW information.
Hope this helps. 73s Laurie.