X10 affecting TV Signals

[travisdh]

Hi All,

Wondering if anyone has had any problems with X10 signals having an effect on their TV aerials, I have in wall modules controlled by a TI213-RS232, and in a specific area of the house, if any modules are turned on (in this area there is a total of three), the digital TV signal goes haywire.

I spoke to a local TV guy, who said moving the aerial will have very little affect since the interference is coming from the house, and when the lights are off, there is no affect.

Wondering if anyone has had something similar, it will likely be the catalyst for me moving to Z-Wave, but i would much rather do a phased implementation, bit by bit rather than having to turn off all 24 X10 modules, if you have had a similar problem how did you get Around the interference?

Thanks

[Wadenut]

That's very odd, since when an X10 powerline module is sitting On or Off (not being actively switched), there should be no activity on the powerline at all unless it's reporting it's status in response to a poll. Even X10-RF operates on a completely different band than TV signals.
In any case, an X10 filter (not sure of the Aussie model #) on the TV power supply should block anything getting through. A UPS powering the TV might have the same effect.
Is there any sound coming from these modules? A chattering relay perhaps? This could generate some RF.
By any chance are you using any X10 (powerline or RF) not intended for your market? RF especially might interfere with other equipment.

[travisdh]

I am using x10 PLC but not RF, interestingly it is when the lights are on.
The modules are designed for my market , I am wondering if a power cable running in the roof or wall is too close to a coax cable

[Wadenut]

I am using x10 PLC but not RF, interestingly it is when the lights are on.
The modules are designed for my market , I am wondering if a power cable running in the roof or wall is too close to a coax cable

Now, that's a possibility. The power lines no doubt will radiate and could affect the TV if run along side the coax (this is never recommended for just this reason).
Does this problem occur without the X10 modules in place and the lights/appliances normally plugged into them turned on? If that's the case, the only option would be to move the coax. You might also want to check all of the connections on the coax. If theres a loose one or a badly connected shield it would be more susceptible. Some of the cheaper coax out there isn't all that well shielded as well. A better grade of coax might help. A foil shield is known as 100%, whereas a braided shield can open when the coax is bent or flexed.

Check too that the antenna itself isn't too close to some AC wiring.

[travisdh]

I will have a look and see if there are cables running near the power lines. To be honest i don't actually know but have a suspicion given the issue only occurs when lights are actually on in a specific area. If it were the PLC system, when other lights were being turned on or off i would expect the same issue to occur, and interestingly, the house is wired to the max with coax etc, when i unplug the unused coax from the distribution hub the signal gets (a little) better, which is what makes me think maybe that is where the interference is coming from.

Hopefully there is enough length in the coax cables to be able to lift them, i was thinking if there is enough length the easiest thing would be to string them from the rafters which should have a fair bit of distance away from the power lines (and try and not have them run parallel).

The coax cable i have is foil wrapped, but i doubt it is the greatest quality cable (next time i will make sure I pick the cable, not let others do that).

[Wadenut]

OK. If there's a lot of coax unused, it needs to be terminated at the free end, otherwise it's an antenna (both transmitting and receiving). [I had a visit from my cable company once because I was broadcasting their signal from an unused coax run]. Even an unused connection on your distribution panel or any splitters shoud be terminated to reduce reflection. 75 ohm terminators are available for this purpose. Your TV guy ought to be able to supply these.

[travisdh]

I went from 9 Connections down to 4 (in use) and the next thing is to terminate the connections that I have removed from the distribution hub. They terminate to wall plates in each room, but i have no idea if that is actually enough, so it is easy enough for me to terminate the connections in the distribution hub. Because i know it is in the kitchen it is pretty easy for me to check the coax in that area and see if there are cables in that area too close to the power cables for the lighting.

It only affects one TV signal (well actually 3, from one broadcaster) which is around the 200 mhz range, right where the interference is apparently.

The most frustrating thing is i know how much cable is there, and its rough path but I was away with work when it was laid, so i have no idea how close it is to power, but i guess the interference suggests too close!

[Wadenut]

I went from 9 Connections down to 4 (in use) and the next thing is to terminate the connections that I have removed from the distribution hub. They terminate to wall plates in each room, but i have no idea if that is actually enough, so it is easy enough for me to terminate the connections in the distribution hub. Because i know it is in the kitchen it is pretty easy for me to check the coax in that area and see if there are cables in that area too close to the power cables for the lighting.

It only affects one TV signal (well actually 3, from one broadcaster) which is around the 200 mhz range, right where the interference is apparently.

The most frustrating thing is i know how much cable is there, and its rough path but I was away with work when it was laid, so i have no idea how close it is to power, but i guess the interference suggests too close!

Let us know the result when you're done. 50Hz is a long way from 200Mhz, but there will be harmonics as well which could get there, especially when 50Hz and 200Mhz mix. It would be interesting to look at it with a spectrum analyser (a rather expensive piece of equipment ) .

I'd go slap whoever installed the wiring.

[travisdh]

I had a TV guy around, who was looking at the reception (at the TV Aerial) with an analyzer, it was completely affecting the signal in that channel range.

The joys of wiring, thankfully i did not install the wiring since i was away, but the installer did a terrible job, the latest guy who determined at least where the fault was very scathing of the work done, the distribution hub was not terminated, the cables between the signal amplifier and the hub were too small, and some of the connections were lose so that had a pretty big affect, fixing some of those things made a difference.

[Wadenut]

That's too bad. At least, I think, you're on the track of solving the problem.
The amplifier deserves special attention. It ought to be as close as possible to the antenna, and its connections need to be tight.
Look at any grounding points as well along the entire coax network. Ideally (and this is a point of contention as there are several schools of thought), there should be only one point of ground otherwise there could be ground loops created which can pick up the AC and induce it onto your TV signal.
Check the grounding at the outlets in question as well. I'm not familiar with Australian AC wiring standards, but here all AC wiring boxes have a ground running directly back to the electrical panel. Given that your contractor seems to have done a rush job, it's worth a look. I've seen a few do-it-yourself jobs that would curl your hair.

All this said, I have one room with a poor TV signal. Now I'm going to have to look at that. I hadn't been concerned as I seldom use that TV.

[travisdh]

Yeah every line normally has a ground in it, i think the only ground point in my coax system (if there is one) would be at the amplifier part i guess, ah well slowly getting there bit by bit troubleshooting.

[Wadenut]

Yeah every line normally has a ground in it, i think the only ground point in my coax system (if there is one) would be at the amplifier part i guess, ah well slowly getting there bit by bit troubleshooting.

It's good experience for you.

You can check the ground at that amp, on the outside of the cable with a multimeter between that point and a nearby AC outlet ground (indeed at any coax connection). Any voltage measured there can indicate a poor ground.

[travisdh]

I got in the roof, and tried the simple fix (moving the cables upwards slightly), they do cross some electrical cables but not as many as i was thinking, given it is 10:50pm here so i didn't look that well.

What did surprise me was that we got a TV put in the bathroom a few months ago (not the surprise), anyways when i was tracing the aerial cable from the roof, and it appears like the installer had split the TV aerial before it goes into the signal amplifier in my structured wiring closet (i.e. all cables run into there), anyway that surprised me that one line goes off to the TV in the bathroom, and the other goes to the amplifier.

The signal amplifier does not actually have a ground from what i can see, it runs the coax into the signal amplifier and distribution hub, then runs out to each room, but at no point (unless in the actual devices) is there a ground, the TV signal amplifier has one of those plug in connections driven from a power pack.

Anyways, i figure looking at shortening the aerial might have some affect, that is removing the split and returning the aerial to just the signal amplifier.

In terms of the ground comment, is it worth looking at grounding say the distribution box, to see if that gets rid of some of the interference? Is it just a case of taking the outer sheeth of one of the coax cables and tieing it into a ground point somewhere, since most devices now days are double insulated and have no ground?

[Wadenut]

Actually crossing the AC lines shouldn't cause too much problem. It's when they run parallel you'll be apt to pick up interference.

You've got to be careful. If there happens to be any appreciable voltage on the ungrounded coax sheath, you might be in for a nasty shock.

I would hope the antenna mast itself is properly grounded for lightning protection. If so, this might be a good place to bond the coax sheath. At any rate, the coax should be grounded for lightning protection if nothing else.

With the amp after the splitter, only one branch of that circuit will be amplified. The first thing I'd try is moving that to before the splitter.
If there's any appreciable distance between the amplifier and the antenna, you could be picking up the noise there. The idea is to amplify the signal, and not the noise by having the amp as close as possible to the antenna.

Wait until morning. You don't want to be falling off the roof in the dark (nor daytime for that matter).

The good ol' days. Antennas on every roof. A rare sight here nowadays.

[travisdh]

also tried grounding the Distribution coax box (outside sheeth) to my Homeseer PC case ground, also no luck with that one, it did make a very marginal difference, i wonder now if the signal coming into the house is not enough to overcome the interference as it was split to the bathroom, and amplifier, and will later try and see what happens when i remove the bathroom TV from the main aerial, maybe it means that the signal increases and gets marginally above the interference (i can always hope).