Any electrical spark creates radio waves and acts as a transmitter. You hear sparks on a radio as interference. That's why lighting makes radios crackle, and even the tiny spark in a switch is enough to make a noise on the radio when turning on a light. Episode Contents: Models: Toilet tube crystal set. Machines: Lovely little (1 metre long) RC car made by Rex for kids show. Guests: A Hertz induction coil and loop reciever. Early Marconi radios. Antique BBC transmitter (c.1920) and it's modern equivalent. Various antique sets and accessories. Films: The cartoon life of young Marconi and an old Armstrong. An ad for 1950 plastic RCA portables. Extro: Motorized novelty radios.