My interests include :

ham radio,

especially tube-type military radios (affectionately known as "boatanchors"),
simple homebrew tube receivers and transmitters ("glowbugs"),
radio direction finding (RDF) or "fox-hunting",
"homebrewing" (designing and building my own radios and test gear),

military history,

especially the history of RADAR and electronic countermeasures,
cryptography, and cipher machines.

camping, and canoeing.