A talk I prepared with the late Alan Hobbs, G8GOJ, for the RSGB Data Symposium in 1987. Presented as three short articles with plenty of illustrations. Extra pictures added and existing ones made bigger November 1999.
The text was revised in 2014 with additions & corrections & newer, bigger pictures. A supplement, Part 4, was added to try to summarise the changes since the main article was written.
These articles © 1987-2014, AG Hobbs & SM Hallas. Pictures © Sam Hallas except where source acknowledged