Could A Stb Downstairs Cause Interference With An Upstairs Tv?

[Was_There_Then]

I am writing on behalf of friends of mine for some advice. They have just moved into a new house in the suburb of Castle Hill in Sydney. They have paid a firm to come round and fit a new aerial and fix up the necessary cabling.

The issue is, they have a stb connected to a tv downstairs. They also have a new tv upstairs with an in-built HD tuner. However, whenever the stb is connected to the downstairs tv (whether it is turned on or not) all of the channels upstairs become very pixelated or frozen. If they then disconnect the stb, the upstairs tv is perfect.

When the aerial guy was doing the work and he noticed this, he told them that the stb was faulty. They took it back to the shop who tested it and said it was fine. They insisted on a replacement anyway so they were given a new one. However, the problem still exists.

So anytime the stb is hooked up downstairs, the upstairs digital channels go on the blink. Disconnect the stb, and the problem is solved.

I’m not too clued up with aerial cabling but could this be a problem with the way he has set up cabling? Apparently he has looped the internal cabling around the house, do you think he has done something incorrectly.

Any help is much appreciated.

[charlesc]

Having devices plugged in or out shouldn't affect other receivers on the same antenna distribution system.

In larger distribution systems, 'taps' are used in preference to 'splitters' because they provide a higher level of isolation, so it really doesn't matter much if the outlets are being used/shorted/damaged etc or not. However even with splitters, you shouldn't be seeing such an obvious problem occurring as reported.

'Looping the cable' sounds a bit unusual, unless he has used taps, when it would be quite normal. It would however be bit unusual to do this in a domestic installation, all the same.

A typical way to cable a domestic installation would be to run antenna cable from individual outlets back to a central point. Then at this central point, a splitter or some taps would be used. That way a problem on a looping cable run is hopefully avoided. And if one outlet is disconnected, you don't loose signal downstream. Cable runs aren't usually that long, in any case.

I saw a job a few weeks ago where the antenna cabling was indeeed looped, but 'gathered' together at one or two outlets. And at those outlets it was just twisted together, as an electrician would do with normal wires. The system hadn't worked very well, needless to say.

I suggest the installer for your friends' house is asked to come back, and investigate the problem. It seems very repeatable. Maybe he bring a couple of his own STBs.

It may be that the signal is a bit borderline, and when the STB is connected it is somehow loading the signal on the distribution system and causing problems. As mentioned, this shouldn't happen.

[mtv]

I agree with charlesc's comments on a possible scenario of 'looping' the cable through the outlets.

If this is the method of cabling used, this will indeed cause a lot of errors in the digital signals and subsequent reception loss.

I too have seen this type of cabling terminations many times.... damn sparkies....... grrrrrrr.

As suggested, have the tech return to investigate further.

Edited September 24, 2008 by mtv

[Was_There_Then]

Thanks for the above responses. I have passed on your info and they are now calling to get him back out.

As I say, I have never heard of an instance where connecting a stb, degrades digital channels elsewhere in the house. I can only assume that the problem is due to his work…

Thanks again