Re: [IRCA] Noisy cable TV

[Rick Kunath <k9ao@xxxxxxxxxxx>]

On Wednesday 04 October 2006 04:48 pm, W. Curt Deegan wrote:
>
> There is a problem, he will write it up for maintenance and in a week or so
> they will check into it.  About all he could or would tell me was that
> there was noise on the line from somewhere.  He said he was surprised no
> one else had reported a problem because the noise should be inducing poor
> picture quality especially on lower channels. 

Yes and no. If the noise is conducted on the *outside* of the shield of the 
cable plant, and the cable plant is ingress tight, then no. It wouldn't 
affect the picture quality, even though it was being conducted along the 
cable plant interfering with over-the-air services. If the noise is a 
byproduct of hardware problems on the plant, then maybe.

>  He removed a dangling
> disconnected piece of coax and tightened the connections at the junction
> box.  Those efforts produced no discernable change in what was already a
> low noise level at the time.

Tightened the tap connections I'd say. A good thing to do whenever you get the 
chance.

> I am less than confident whatever maintenance does, will address my real
> problem with radio and DSL interference.  Indeed, they may end up boosting
> the cable signal and thereby produce even more noise. 

Folks think a line tech can just crank up the gain on a CATV system. He can't. 
The system is designed to work with a certain engineered level. He'll have to 
get it there if it isn't. Fairly minor changes will wreak total havoc with 
the downstream cascade. Even changing tap values to boost a particular 
subscriber's signal really requires a re-design because all downstream levels 
will then be way off.

> But until they fix 
> the problem they know they have, I don't expect them to listen to my
> issues.  Who knows, maybe they are related and all things will turn out
> wonderful. :-\

This may be a CATV aerial plant power supply problem. Mention that when your 
line tech gets there. He can kill the AC feed to the supply and let it run on 
batteries to see if the noise goes away. It still may be internal even on 
batteries.

Schedule a later appointment if you can. And if you get nowhere, find out 
where your nearest local dispatch shop is and pop in to see the CATV plant 
manager. Explain to him what the problem is and how to duplicate it.

>
> Anyone who is interested can retrieve the file here (upper/lower case is
> significant):
> http://scooterhound.com/WWWR/radio/CableTVNoise.mp3

Can you tell if the noise is 60 Hz related at all, or some other frequency 
pattern? Spectran, Spectrum Lab, maybe some other way?

Rick Kunath
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