VHS has two different audio tracks - why?
 

https://youtu.be/B80_fuJ7yrI

You know that VHS tapes have two separate audio tracks (stereo and mono). Normally when the stereo track is corroded I just switch to the mono track when digitizing. But THIS time, SOMEHOW, something completely different was recorded to the mono track. It appears to be some kind of weather radio channel....?

In terms of value this tape is priceless -- I've digitized hundreds of tapes and never run across this kind of quirk before. As an archivist, though, this tape sucks -- neither track is any good, so I can't win either way.

The problem appears to have been from the cable provider -- only programs recorded from certain stations that day turned out like this. ABC has a weather station, NBC has silence and CBS has....CBS from earlier in the day. Other channels turned out fine.

Have any of you ever heard of such a thing? What could have caused this?

This also might be a good opportunity to ask, once again, if anything can be done about distorted hi-fi tracks like this one.

With bad HiFi audio I find that unless the tape is physically damages (wrinkled, creased, worn out) then the HiFi is readable if you take certain steps such as try another VCR - older HiFi decks (1999-1992) are usually better at tracking than modern ones. I also have a 1991 Panasonic NV-F65 VCR which I have modified by drilling holes in the top with home made adjusters to adjust:

Tape guides
Switch point
Audio azimuth

so that I can play almost any tape. The in and out guide have a big effect on audio and video tracking and I set the switch point for each tape so that none of the bottom of the image is corrupted by the usual switch point. This was a very old, corrupted and noisy tape but it responded well to manual adjustments. https://www.youtube.com/watch?v=nDdX2xKTAGM

Yes I think I can answer why. There are two audio tracks, one is Hi Fi, which is recorded helicaly like the video, the other is called linear, which can actually be stereo and have dolby, though decks which handle that are rare as they were obsoleted by the Hi Fi feature.

The reason they would be separate, is if they were recorded from the tuner originally, and designed so that the SAP (Second Audio Program) was recorded to the linear tracks. The SAP was an important standard for over the air 2nd audio track, to handle Spanish in the US, or descriptive audio for the hard of hearing. I believe some stations just put weather/news on it.

Even 6 years ago, before my area went digital, I heard descriptive audio on my TV, and it was useful as it explained what was going on in TV shows better that you could figure out yourself, because they have knowledge of the script I think.

You could actually store 4 analog tracks, and with a PCM recorder, 2 more digital tracks. I thought of recording a movie with modern 5.0 sound using dolby for the 3 main tracks on the Hi Fi and linear audio for the surrounds, it would probably work pretty well. Besides that, record a widescreen movie anamorphically and you could get quite a bit more out of an old analog system.