Tungsten lamp VHF (Low) and FM band interference.
 

Here's an exquisite thread from Joe Sousa explaining why the occasional "squirrel cage" tungsten lamp still in use circa 1946 could have caused interference on the low VHF TV band and FM radio band.

This phenomenon was well documented in period servicing guides and manuals, so it did in fact cause grief for TV viewers back in the late 1940s, but was seldom explained, and never explained as eloquently as this:

http://www.radiomuseum.org/forum/rus...surements.html

Interesting... Who'd a thunk it?