Expecting FM broadcast quality audio from a TV audio signal is like > trying to record a song by holding a cassette recorder up to a > radio. Sooner or later, those who attempt it have to admit that it's > not a productive approach.
Oh, come on Bill, it's not that bad!
Back when I was working in cable TV, we used to offer a cable FM service. We transmitted standard BTSC (or monaural) RF carriers down the FM band, and connected the cable directly to the customer's FM radio. A bit noisy, but certainly not as bad as holding a cassette recorder up to a radio!
We even carried TV aural as part of the cable FM service. The headend gear included frequency-tripling circuitry to change the deviation from
+/-25 to +/-75. I posted a description of the process back in 2003 at
formatting link
down to "The Rise of Cable FM".
Neal McLain