Today I completed breadboarding a very basic TX down-converter which takes a 28MHz signal from the FT817 and produces around 700mW out on 500kHz at the TX 50 ohm output. When connected to my random 15m long wire antenna the ERP is just microwatts so real QRPpp. I have managed to match my wire antenna with a tapped coil on a ferrite rod and a variable capacitor as ATU. At this stage it is not the massive loading coils that you see in the pictures of "proper" 500kHz stations but this will have to come if I am to make any real progress along with more power.
This evening I've put this TX on the air on 500kHz WSPR, more in hope than expectation! It is just possible that some of my near local 500kHz stations (around 40-60kms away) might just manage to decode me at around -30dB S/N on WSPR. A test is planned with G6ALB a few miles away on Tuesday evening when I shall try both CW and WSPR transmissions.