JVC HRXVC44U DVD/VCR combo and seeing scan lines

Hello Experts:

I recently purchased a JVC HRXVC44U DVD/VCR combo unit (has
progressive scan) with the intention of getting a few years out of it
before I buy a HDTV (I didnt want to buy one now because I want one
with a built in decoder when all channels go HD and the prices come
down).

Anyways, I have an old (10-15 yrs) Magnavox 27" television with only
Antenna and Coaxile imputs. That being said, I am using COAX from the
cable-co to the JVC, out to the Cable Box and from there to the TV.
All works well (signal wise and picture wise) when the JVC is OFF.
However, When the JVC is ON (not even playing a DVD or VHS tape) I see
scan lines on the TV screen. They are not consistant however..
sometimes they are there going top to bottom, sometime bottom to top,
and the speed also varies. I have been told that if it is the JVC then
I would see more static, but the picture quality is actually quite
nice except for the annoying scan lines.

Has anyone else had this happen? I am not sure if I should send the
JVC back or if I can adjust the rate of scan (??) on the television to
compensate for the JVC. Just for the heck of it I turned ProgScan on
but of course the screen becomes all snow. COuld this be the COAX?

Thanks!