Radios
From an early age I built crystal sets then repaired five valve radios. While still in primary school I had mastered the secrets and practicalities of the superheterodyne.
And by early high school I had an unlicensed ham radio; an old No19 tank transceiver, surplus from the War, that I modified extensively; removing the very high frequency section and adding a power supply; in an attempt to communicate with radio amateurs overseas.
Although I could easily communicate with the school cadet radios and our own walkie-talkie, making myself heard overseas proved elusive; despite increasingly long and elaborate aerials.
The basic short wave transmitter was based around one of the famous 807 transmitter valves that delivered about 8 watts.
When I tried amplifying my signal to around 50 watts (four 807s in push-pull); enough power to light a florescent tube held near the aerial, I broke into the local TV signal in the surrounding area; to the consternation of the neighbours.
I promptly shut everything down; but lived in fear of the PMG inspectors for about a month. The Postmaster General's Department was at that time responsible for allocating, regulating and policing the radio spectrum. Hunting down illegal users,apocryphally using direction finding vans, was a specialty; probably a remnant of wartime spy-catching.
There was as yet no Citizens Band (CB radio) allocated and today's mobile phone bands were in the even more distant future.
I'm not sure how many people were affected. TV sets, black and white of course, were expensive luxury items and it was said, perhaps maliciously, that certain people bought a roof aerial, the outward appearance of TV possession, before actually possessing a set.