Cable interference from OTA digital signal

[Keith_Lake]

My house is in direct line-of-sight with the local PBS transmitter site. Ever since they turned on their channel 26 digital signal, the cable channels above 70 are mostly wiped out and unviewable. It's probably some frequency harmonic/mixing thing.

I sent an email to the CE and he was kind enough to come out here with his signal meters and test equipment. He had the operator back at the station bump the carrier off briefly. During that second or so, the cable channels above 70 were crystal clear.

We traced the problem to the short cable connecting my VCR to the reciever.
When the incoming cable TV line is connected directly to the TV, bypassing the VCR, the interference lessens but is still evident onscreen.

I'd rather not have to move wires around to switch between the cable and the VCR. I've tried several different brands of shielded cables between the VCR and the TV with no visible improvement. What next? Ferrite beads?

KL

<a href="http://home.nc.rr.com/gttyson/lastradio.html">The Last Radio Station<a>

 

[Les]

> We traced the problem to the short cable connecting my
> VCR to the reciever.
> When the incoming cable TV line is connected directly to the
> TV, bypassing the VCR, the interference lessens but is still
> evident onscreen.

The cheap cable with slide-in "F" type connectors usually
supplied with VCR's and DVD players is the cause of a large
majority of the intereference problems seen in the world.

> I'd rather not have to move wires around to switch
> between the cable and the VCR. I've tried several different
> brands of shielded cables between the VCR and the TV with no
> visible improvement. What next? Ferrite beads?

These things are additive. The cable company probably supplied
some decent double (at least) shielded cable to get to your
cable box or VCR. Likely it's also grounded, as required by
National Electrical Code, just before it enters the house.

If it ISN'T grounded, hound the cable company to do it. It
may or may not help your problem but it will help you collect
on your homeowner's or renter's insurance if you ever have
a fire.

If you're using a cable box, the cable between it and the
VCR and from the VCR to the TV need to be of the same
quality as that provided by the cable company. That means
properly fitted screw-on "F" connectors...none of that
slide-on junk.

Ferrite beads aren't gonna help but I believe you may be
thinking of ferrite toroids, available at any decent
electronics shop. Kinda of donut like dark gray in
color. Choose a diameter that will allow you to wrap your
coax around the outer ring several times. Wouldn't hurt
to put one on each piece of cable (outside/cable box,
cable box/VCR, VCR/TV, etc.). Not probable to help but
now and then it helps to wrap the power cord of each
device around a toroid.

If others in your building or nearby aren't having this
problem it's possible your TV or VCR is being front-end
loaded. Sometimes grounding the chassis helps but
I'm not sure about NEC implications. Sometimes, inside
stations, I've lifted the line-cord ground and directly
grounded the chassis of various devices to the station
(earth) ground. This definitely ain't NEC compliant but
it has worked on stubborn cases.

Good Luck!

<P ID="signature">______________
Yes, and even the fleas on their children's pets, the cockroaches under their sinks and the fleas on their camels.</P>

 

[vtjazy]

> My house is in direct line-of-sight with the local PBS
> transmitter site. Ever since they turned on their channel
> 26 digital signal, the cable channels above 70 are mostly
> wiped out and unviewable. It's probably some frequency
> harmonic/mixing thing.
>
> I sent an email to the CE and he was kind enough to come
> out here with his signal meters and test equipment. He had
> the operator back at the station bump the carrier off
> briefly. During that second or so, the cable channels above
> 70 were crystal clear.
>
> We traced the problem to the short cable connecting my
> VCR to the reciever.
> When the incoming cable TV line is connected directly to the
> TV, bypassing the VCR, the interference lessens but is still
> evident onscreen.
>
> I'd rather not have to move wires around to switch
> between the cable and the VCR. I've tried several different
> brands of shielded cables between the VCR and the TV with no
> visible improvement. What next? Ferrite beads?
>
> KL
>
> The Last Radio Station
>

My grandma has a similar problem, except it's analog ch 3 from Tijuana (I think) ghosting over ESPN. I tell ya, it's hard to watch the holiday bowl games when you have a mexican network bug floating all around your field of view...