Re: Think of the Children!
You can get audio at the difference frequency between Video and Audio carriers, and harmonics, so 6MHz, 12MHz, 18MHz etc for 625 TV. About 4.x something MHz on 405, long time ago, I don't remember.
The Audio IF strip if on carrier rather than "intercarrier" is 6MHz below video IF usually, so about 33MHz approx for 625 line.
USA used 44MHz Video IF and Europe usually 39MHz approx for 625 line. Earlier 405 sets used various frequencies from about 12MHz to 44MHz. Earliest 405 sets simply tuned one 42MHz approx channel directly with NO IF, later in 1955 the first set boxes sold for Band I only sets to get ITV on Band III