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  • BobT
    replied
    Originally posted by travisdh View Post
    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?
    It appears your installer didn't have a clue on proper coax installation. "Splitting" the coax from the antenna to the amplifier causes a major mismatch in the antenna cable. Antenna coax mismatch can cause a "stub trap effect" which could effectively short out your digital TV signals across a relatively wide frequency.

    If you can access your coax system and remove that split, test your X10 system again for interference. If your TV interference disappears, you have found the cause.

    Leave a comment:


  • Pete
    replied
    The topic of grounding; surge protection (yes a bit of a tangent) became a very long thread here:

    http://cocoontech.com/forums/topic/1...rge-protector/

    Personally I had gotten a great deal on a commercial Eaton surge protector and went really slow (baby steps) installing it. That said the surge protector had no holes on it to feed the power out of it. I didn't think of using a hole punch but rather just busted a couple of drill bits drilling a 3/4" hole into the case to connect it on the side of my fuse panel. The specific Eaton I purchased has connections to the HAI OPII panel and optional intelligent displays built in. (way overkill for a residential installation but it has a 20 year free replacement warranty).

    http://www.sinewavetechnologies.biz/...PT160-SPEC.pdf

    BTW the whole TV thing (here in my home) is migrating from the aerial RG6 connection to the TV to one head end box with multiple tuners/multiple clients connected now via network for live streaming and channel changing; easier to deal with than multiple RF connections. (similiar in fact to the Sage TV thing).
    Last edited by Pete; August 26, 2012, 01:31 PM.

    Leave a comment:


  • Wadenut
    replied
    Originally posted by travisdh View Post
    Actually when i was removing some of the unused coax i did get a few minor tingles, very low voltage (i have a good internal voltage gauge, having received shocks from 12V all the way up to 50,000V - Given low current) which fits with you earth comment. In terms of grounding, i could be totally wrong but on my last few visits to the roof, i didn't note any grounding for the TV aerial, i think in terms of Australian code it is actually optional, and to that extent at any aerial i have seen it is quite uncommon to ground it, (could be wrong, but i know in my case, it is not grounded, as the only cable that runs down from the roof is the coax).

    In terms of the actual amp, it is one of the amplified boxes, that actually has the amplifier (power injector) at a seperate part of the circuit, so in this case the amplifier part is very close to the distribution hub, with the system going:


    Aerial
    |
    Splitter ----> Bathroom TV
    |
    (UHF / VHF etc Input of amplifier)
    |
    Kingray style amplifer
    |
    (Output of amplifier)
    |
    Splitter ---- > Power Injector (to power above amplifier)
    |
    Distribution Hub --> to three connected TV's
    Ouch!
    From what Pete mentioned, you can see why grounds (earths) are important. A lightning strike or near miss could take out all your equipment at the very least, and at worst, well... blow your roof off. It's hard to believe until you've seen the result of a direct strike.
    Aside from that, grounding the coax at some point will not only help improve things, it'll aford some protection.

    Yes, splitting the unamplified signal is resulting in amplifying 50% of the original, which is fine if there's a strong signal in the first place. Moving the amp to before the splitter will help on both branches.

    Leave a comment:


  • Pete
    replied
    Here I got a bit paranoid relating to the whole grounding thing after a lightning bolt took out my Rain8nets. I was lucky cuz the lightning took out LCD TVs and kitchen appliances, alarm panel etc next door. Just an environment for lightning in the air can cause some issues. Goofing around (very dangerous) setting up an aerial once; before grounding and before a storm saw sparks more than 12" to a nearby electrical outlet once. Very interesting little light show.

    I do have multiple earth grounds connected to my electrical panel and other stuff (like the aerial cables). The base though was that the electrical panel is grounded to a water pipe and multiple earth stakes.

    My OTA TV antenna is mounted in the attic. I do have an in house video set up which is a carry over from many years ago. Today its a mixture of broadcase HD and SD on the LCD TV's. I did have power injectors in place for IR repeating and have removed them.

    So here I have:

    Aerial ==> amplifier (20 feet or so from aerial in attic / powered 120VAC)
    ==> combo channel injectors (basement - all grounded) ==> distribution amp with terminators on ends not used ==> TV's that use OTA/in house stuff.

    It was a hodgepodge though of OTA, Cable and satellite feeds. (even using a Nexus-S card in a PC a while ago).

    Many years ago the quick and easy way to "hear" harmonics was to utilize an AM transistor radio tuned between radio stations. I used to use this for my automobiles.

    Leave a comment:


  • travisdh
    replied
    Originally posted by Wadenut View Post
    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.
    Actually when i was removing some of the unused coax i did get a few minor tingles, very low voltage (i have a good internal voltage gauge, having received shocks from 12V all the way up to 50,000V - Given low current) which fits with you earth comment. In terms of grounding, i could be totally wrong but on my last few visits to the roof, i didn't note any grounding for the TV aerial, i think in terms of Australian code it is actually optional, and to that extent at any aerial i have seen it is quite uncommon to ground it, (could be wrong, but i know in my case, it is not grounded, as the only cable that runs down from the roof is the coax).

    In terms of the actual amp, it is one of the amplified boxes, that actually has the amplifier (power injector) at a seperate part of the circuit, so in this case the amplifier part is very close to the distribution hub, with the system going:


    Aerial
    |
    Splitter ----> Bathroom TV
    |
    (UHF / VHF etc Input of amplifier)
    |
    Kingray style amplifer
    |
    (Output of amplifier)
    |
    Splitter ---- > Power Injector (to power above amplifier)
    |
    Distribution Hub --> to three connected TV's

    Leave a comment:


  • travisdh
    replied
    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).

    Leave a comment:


  • Wadenut
    replied
    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.

    Leave a comment:


  • travisdh
    replied
    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?

    Leave a comment:


  • Wadenut
    replied
    Originally posted by travisdh View Post
    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.

    Leave a comment:


  • travisdh
    replied
    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.

    Leave a comment:


  • Wadenut
    replied
    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.

    Leave a comment:


  • travisdh
    replied
    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.

    Leave a comment:


  • Wadenut
    replied
    Originally posted by travisdh View Post
    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.

    Leave a comment:


  • travisdh
    replied
    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!

    Leave a comment:


  • Wadenut
    replied
    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.

    Leave a comment:

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