I just got a new TV. A Memorex MT2024.
I don't have cable or anything,
The TV is connected to a VCR which is connected to
a powered amplifier box. The box's other output
is connected to a small TV in another room. The input
is connected to the apartments ( common ) roof antenna.

Now the first few years of using it with my old TV, the roof antenna
seemed to work fine. In the fourth year, during heavy rains
some UHF stations would have poor reception, up to the point
where they became unwatchable. When my upstairs neighbor
did some renovation that problem seemed to suddenly go away,
but a new one showed up.

Most of the stations would be fine.but two would sometimes
be good and sometimes be bad. Like they were picking up some noise
from some electrical appliances. My other TV seemed to have problems
too experience. That's when I got the powered amplifier. That seemed
to help but didn't fix the problem completely.

Sorry for all the background. I just wanted to be thorough. Here is
my problem. On some channels, there is a horizontal band maybe
1cm thick. It starts at the bottom and scrolls up (takes about 5
seconds). I looks like someone tied a string to the right side of the
tv and pulled at the band. It's obvious on the stations that get bad
reception, a little less obvious ( but still obvious) for stations
that get very good reception but not perfect reception.

For stations with perfect reception, the band is still there but it
looks different. It looks like a decrease in the brightness settings
for the width of the band.

Before I noticed this problem, I spent a couple of hours watching
a tape and was toggling the tape and live sports. I noticed the
bad image after I shut off the VCR. I can't say whether it was there
before or not. The thing is that I see this band only when I am using
the TV's tuner. When I use the VCR's tuner I don't see it.

After a while I tried disconnecting the TV from the VCR and plugging
in an old TV antenna, the effect mostly goes away. I say mostly,
because if you look carefully you can see slightly darker bans
scrolling up the TV. It is a little more visible during dark scenes,
or when the TV goes black. Then you see a pattern of black and
slightly less black scrolling up the screen.

The thing I need most is to figure out whether or not this is the
fault of TV, since if I take it back I want to do so as early as
possible.
Knowing exactly what is wrong would help. Any kinds of tests
( like connecting an old antenna ) that help me narrow down the
problem. If it's not the TV but some kind of TVI figuring out what it
is ( and hopefully how to get rid of it ) would be a big help. Should
I replace the amplifier box?

Thanks