Problems Capturing from Cable with ADVC-100

[TheUglyDuckling]

Recently, I split my cable (television) line in order to be able to digitally cap the signal with my ADVC-100. I lead the new RF cable into the back of the Sony VCR which is located next to my computer, and the signal goes out through the composite video out jacks and into the ADVC-100, just like it would when I am backing up VHS tapes.

Everything seemed to work (at first glance), but it became readily apparent that the incoming signal had a great amount of interference -- a low hum was present in the audio, and the video waved slightly. This surprised me, since I'd used a shielded RF cable, but it did not seem to be a completely unreasonable to assume that the cable line was picking up interference from other cables.

Now, if the problem was as simple as my cable line picking up interference from the power cables under my desk, I would not be confused. However, now that I've connected the cable signal to the back of my VCR, the signal from VHS playback (which was fine before, and shouldn't be dependent on the cable signal) is affected by the same interference. Am I wrong in thinking that this shouldn't be happening, since the VHS playback should not be affected by interference from the incoming cable signal?

Has anyone experienced a similar problem, or does anybody have any idea how to fix it? Might a different VCR resolve these issues?

Thanks in advance,
TheUglyDuckling

[Video Dude]

That sounds like it might be a "ground loop", also known as "hum bars".
Do a Google search if you want learn the technical details of what it is.

A CATV Isolator might help.

How do you know if the "ground loop" is caused by the cable wire?
If when you hook the VCR up to the ADVC-100 with the cable wire NOT connected there is no interference. But as soon as you connect the cable wire you get interference.

This is what your setup will look like:

Cable Wire -> CATV Isolator -> VCR -> ADVC-100 -> PC