Mailing List Archive

> However this is all somewhat spoiled by a horizontal sweeping flicker -
> about 3 'sweeps' per second. It's a bit like what you see when you see
> computer monitors on TV, except it's a vertical lines moving in a
> horizontal sweeping motion.
>
> Anyone got any idea what's going on and how to fix it? Or how I can go
> about
> finding out?

Could be a problem with noise on your cable (from your cable provider),
or from your antenna. I had exactly the same problem here.

Try connecting a wire from the shield of your cable to "ground". Just
about any wire will do, like spare speaker wire, etc. If you use a cable
splitter you can attach the wire to the splitter chassis (anywhere on
the outer metal box). A good place to find "ground" is the screw that
holds the faceplate of an electrical outlet to the electrical box behind
the drywall.

Good luck,

Steve

On Tue, 2003-04-22 at 13:35, Dave Weaver wrote:
> However this is all somewhat spoiled by a horizontal sweeping flicker -
> about 3 'sweeps' per second. It's a bit like what you see when you see
> computer monitors on TV, except it's a vertical lines moving in a
> horizontal sweeping motion.

I had similar problems but with horizontal lines moving in a vertical
direction.

From the research I did, it seems this is referred to as banding (at
least in my case), and is caused by noise picked up by your cables. In
my case, there were four primary sources of noise:

1) a hub I had sitting near the rest of my equipment - when turned on,
it severely interfered with the cable TV signal. The kind of
interference varied depending on the channel. Solution: get rid of the
hub.
2) if you have a cable tv signal or tv antenna plugged directly into
your TV, the ground on that connection can interact with the ground on
the cable connected to your computer, and cause noise in the image.
Solution: unplug the cable from the tv, since I'm using myth to tune
channels now anyway
3) I had a splitter on my cable connection so I could connect both my
vcr and my myth box to the cable signal. When I connected the myth box
directly, bypassing the splitter, the picture improved significantly.
4) I had bought a new NVidia Ti4200 card for my myth box. While trying
to solve my noise problems, I noticed a small improvement in signal and
picture quality when I tried my old NVidia MX440 card.

I also managed to add a lot of noise by trying out a different S-Video
cable.

I would suggest:
1) turn off every electric device you can, hopefully leaving just your
TV and computer running. If that improves the signal quality, turn
devices back on, one by one, to see which ones contribute to noise
2) eliminate as many device interconnections on your computer and TV as
possible. Start with only the power cords, and the video connection to
the TV. Then gradually add more connections, starting with the cable
signal to your tuner card. Take note of how each added connection
affects the picture quality.
3) avoid running any cables near any of your device power supplies as
much as possible

If you can narrow down where the noise is coming from by trial and error
and process of elimination, you might find that all you need to do is go
out and by a cable with better shielding to solve your problems.

Rick

Rick,

That is some good advice. The only thing I would add is that electrical
cables in the wall can also broadcast a lot of noise. I used to have my
monitor next to a particular wall in my old house and it had lines and
such, but then when I moved to my new house it went away. So if you
turn everything off and still have problems then try setting it up on
the kitchen table.

schu

Richard Lee-Morlang wrote:
> On Tue, 2003-04-22 at 13:35, Dave Weaver wrote:
>
>>However this is all somewhat spoiled by a horizontal sweeping flicker -
>>about 3 'sweeps' per second. It's a bit like what you see when you see
>>computer monitors on TV, except it's a vertical lines moving in a
>>horizontal sweeping motion.
>
>
> I had similar problems but with horizontal lines moving in a vertical
> direction.
>
>>From the research I did, it seems this is referred to as banding (at
> least in my case), and is caused by noise picked up by your cables. In
> my case, there were four primary sources of noise:
>
> 1) a hub I had sitting near the rest of my equipment - when turned on,
> it severely interfered with the cable TV signal. The kind of
> interference varied depending on the channel. Solution: get rid of the
> hub.
> 2) if you have a cable tv signal or tv antenna plugged directly into
> your TV, the ground on that connection can interact with the ground on
> the cable connected to your computer, and cause noise in the image.
> Solution: unplug the cable from the tv, since I'm using myth to tune
> channels now anyway
> 3) I had a splitter on my cable connection so I could connect both my
> vcr and my myth box to the cable signal. When I connected the myth box
> directly, bypassing the splitter, the picture improved significantly.
> 4) I had bought a new NVidia Ti4200 card for my myth box. While trying
> to solve my noise problems, I noticed a small improvement in signal and
> picture quality when I tried my old NVidia MX440 card.
>
> I also managed to add a lot of noise by trying out a different S-Video
> cable.
>
> I would suggest:
> 1) turn off every electric device you can, hopefully leaving just your
> TV and computer running. If that improves the signal quality, turn
> devices back on, one by one, to see which ones contribute to noise
> 2) eliminate as many device interconnections on your computer and TV as
> possible. Start with only the power cords, and the video connection to
> the TV. Then gradually add more connections, starting with the cable
> signal to your tuner card. Take note of how each added connection
> affects the picture quality.
> 3) avoid running any cables near any of your device power supplies as
> much as possible
>
> If you can narrow down where the noise is coming from by trial and error
> and process of elimination, you might find that all you need to do is go
> out and by a cable with better shielding to solve your problems.
>
> Rick
>
>
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