[Bob Andersen]

I haven't used my Emerson all that much, but I don't recall it have the issues you describe. The quality and strength of the signal source is definitely a factor. I've had trouble with over the air ATSC to NTSC converter boxes. Hum, noise and sound quality mostly.

They did change the relative strength of the video and sound carriers over the years. The sound carrier was stronger back in the 40s than in more recent times. More expensive modulators like Bonder Tongue allow you to adjust the carrier strengths to compensate.