Hello Mal,

I've wound an air-cored loading coil of about 1.3 H
It's on a wooden frame with hexagonal ends (all yacht varnished) and has a mean diameter of 2 feet.
The winding length is 20 inches and it resonates my 40m inverted 'L' at the correct frequency of 8.97 kHz

I've made a VLF exciter which generates the drive frequency and interfaces with the PC's software.
It uses a 2297 kHz crystal divided by 256 and gives a square wave output for the PA FET's.
I can run CW, QRSS or DFCW with 0.05 Hz shift.

For the TX I've modified my existing 200 watt 500 kHz PA and for matching use an ex-UPS transformer.
The PA seems quite efficient into a 2000 - 3000 ohm resistive load.

I have yet to be picked up beyond the boundary of my own garden so would be over the moon if anyone else can detect my signals.

73 Chris
G3XIZ