Horrible Interference, need isolation/cabling suggestions

Discussion in 'Home Theater Projects' started by Matt^K, Sep 19, 2004.

  1. Matt^K

    Matt^K Auditioning

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    DISCLAIMER: I'm an electronics/hometheatre newbie, so I might be beating down the wrong path here. This is why I'm including so much info, so that if one of you HT Wizards notice something in my description that isn't consistent with normal RF interference, you'll speak up and save me from wasting more time on what might be a different problem entirely; sorry for the long read!

    Hi,

    I currently live a couple hundred away from a series of radio towers that seem to be wreaking havoc on the analog inputs and causing a ton of interference on my Sanyo HT32744 set.

    The towers have always been problematic for me, even before I got a television: pretty much all the speakers in my house (my pc speakers, the speakers on my housemate's VEGA, etc.) "pick up" an FM country music station, which I'm assuming is being broadcast from one of these towers across the valley. I'm pretty sure that one of the towers is broadcasting a high-def signal as well; I don't have an antenna hooked up to this Sanyo, but that hasn't stopped me from receiving digital channel 10-1 at 50% reception. There are also cellular phone towers on the hill; point is, I'm getting bathed in a ton of wavelengths from the towers, and while they have probably rendered me completely sterile by now, I have a couple more years till I have to be worried about that and my first concern is getting a clean signal from my analog outputting devices to my tv.

    The interference is always present over the analog components at any resolution (I'm using the official component cable for the Nintendo Gamecube and some components made with Belden 1694A's from bluejeans for the DVD player), but the interference is much more noticable at 1080i (component upconversion on my Zenith DVB-318). Its hard to describe the interference: its like a bunch of dancing sine waves that has been rotated 90 degrees. Usually it is only noticable on darker scenes in movies and games, but if I look really close and hard it is visibile on almost any scene.

    I think the problem is definitely the cables, or perhaps with the analog devices themselves (my Nintendo gamecube and the Zenith DVD): if I hit the "Freeze Image" button on my TV remote, the interference stops right in place (if it were a problem with the sanyo, the interference would keep "dancing" I'm assuming). Also, Digital Television doesn't have this interference (I did a split-screen comparison via the set's PAP between the one digital channel I get without the antenna and the DVD player's 1080i over component; the interference was solely on the component input).

    I'm stuck using the official gamecube component cable unless I want to crimp my own or something, but as I stated before I'm using a "Belden 1694A, 4 foot" component from bluejeans with the Zenith DVB-318. According to their website, it is "shielded with a dense tinned copper braid and with Belden's "Duofoil" two-layered foil for maximum isolation from outside noise and interference."

    Well those triple layers aren't doing me that much good; I'm getting the same interference on my (comparitively) crappy gamecube cables. Are there other cables out there that might have better resistance against interference that I should try? Or am I just pretty much SOL and am going to have to build a 6-inch thick lead wall around my house and/or drop $300 on a DVI-switch so I can use DVI for everything?


    PS-
    Again, as I said in my disclaimer, I'm really doing a trial-by-fire on all of this and my assumptions might be COMPLETELY wrong; it might not be the towers on the opposing hill at all. Here's a short list of other things I've tried with no luck:

    -Turned off all other devices in the house, including an old refrigerator outside my room
    -Made sure all the devices were hooked up to the same circuit/wall socket
    -Switched between component-2 and component-3 to make sure the problem wassn't just a single bad input. Also verified that the problem exists even over composite video.
    -Switched DVD players (but again, the problem exists on my Gamecube as well so I'm pretty sure its analog devices in general)

    Thanks in advance guys!
     
  2. Chu Gai

    Chu Gai Lead Actor

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    I'd hate to see you spending money trying this idea then that one and finding out the only thing happening is that your wallet is lighter. I'd begin first by finding out if any of my neighbors are also experiencing the same problems. If so, the facility should be made aware of what's happening because they just might have a problem on their end. While you're doing that, try disconnecting the incoming cable from your equipment and see if playing DVD's, games, CD's, still results in these problems. Then, let's take it from there with approaches that if they don't work, you can always get your money back.
     
  3. Matt^K

    Matt^K Auditioning

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    Thanks for the reply,

    Unfortunately I do not know any of my neighboors all that well so I'm a bit uncomfortable just knocking on their front doors and asking them "hi, how's your reception?", but I will try that tomorrow.

    I live in a house that I'm sharing with a couple other guys; all of them are experiencing the same problems with their video devices. I'm the only one with a HDTV and who is (relatively) concerned about picture quality; my housemate with the Vega has this intereference on his 32" but never noticed until I pointed it out myself.

    All of this interference is without CATV plugged into the TV at all; its just the TV connected to the DVD player and the Gamecube, and all the devices are hooked up to the same outlet via a power strip (which I have determined is not causing the interference). I think this effectively rules out a ground loop problem.

    Interestingly, there is one analog video device that I am not recieving any interference on.... the monitor upon which I am typing this post! Its a 19" Samsung SyncMaster900nf hooked up with a basic VGA 15-pin connector. It is running at 1600x1200x32bitx75hz which I'd think would be stressing the cable's bandwith a bit, but as far as I can tell with my eyes, the resulting image is clear as day and has NONE of the (very obvious) interference that I'm getting on my TV only 5 feet away.

    If the problem with the analog components on my TV is an RF interference issue... can anybody explain why I'm not seeing the same issues on my analog monitor?
     
  4. Chu Gai

    Chu Gai Lead Actor

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    So, tell me about your cables and whether you're using any sort of surge protector with your system. Are the cables old, new, how do they look, what about the cable going into your TV..is that a push on or twist on connection. Stuff like that. Never going to know your neighbors if you don't try, right?
     
  5. Matt^K

    Matt^K Auditioning

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    I'm not using any form of surge protection; I have an old powerstrip that all my components are plugged into (the tv, the gamecube, and the dvd player), but I have ruled that out as the cause of interference.

    The GC is hooked up to the tv by the "official" Nintendo GC component cable. Judging from the thinness of the wires, I doubt it is a very high quality product but in most cases I'd assume its sufficient for gaming.

    The DVD player is hooked up via brand new component cables from bluesjeans built using Belden 1694A coax.

    Both plugs have "push in" connections. The bluejeans cable is terminated with Canare RCAP's.

    Let me reinterate that the interference is exactly the same across both cables; the "rotated sine waves effect" appears on both the (presumably) shoddy GC cable and the (presumably) higher-end bluejeans cable.

    I've asked 4 of my neighboors so far if they've been having strange interference problems on their televisions, but none of them said they noticed any. None of the people I asked has a HDTV though, and as I said earlier my housemate never noticed the interference on his Vega until I pointed it out to him, so I'm not sure if my neighboors are accurate in their assessments of their picture quality either.
     
  6. KurtBJC

    KurtBJC Agent

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    Problems like this can be really vexing. The issue, unfortunately, is often that the equipment itself is poorly shielded. In the bygone days when I learned electronics, it was still common to see TV sets with a full steel chassis, and nothing exposed above the chassis surface except the tubes, the harness to the CRT, and in some cases the barrel tuning switches. Now, hardly anything is built with a full chassis, and the outer cases are typically plastic. The consequences for shielding effectiveness are enormous, as most equipment now is darned close to being completely unshielded.

    When you're in a really high RF environment, there's no single answer. The first question is where the interference is getting in. I might try plugging in some other display--if, say, you have a little 13-inch TV in your kitchen, bring it over and see if you get the same interference. If so, the issue is probably upstream; if not, the issue may well be with the display itself. I would probably try consulting with the broadcast station and seeing if they have suggestions; in some cases, they'll provide things like low-pass filters for free, which may or may not help your situation, depending where it's getting in.

    While I suppose I have a vested interest in saying so, so you can take it for whatever you think it's worth, the cables are probably easily your strongest link in the chain because they're fully enclosed and have the most effective shielding available on any stock video cable of reasonable size--better than quad shield and other configurations you may have heard about.

    The fact that you're seeing the interference only when viewing analog sources, by the way, does not mean the display isn't the problem. Your DVI input runs, part of the way, through different circuitry than the analog inputs run through, so it's entirely possible that the problem is at the input stage of your display, but only in the analog side. Often one really never does figure out what the issue is, even when it's resolved.
     
  7. Chu Gai

    Chu Gai Lead Actor

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    I only mentioned the surge protection not so much for that, but because they invariably have some EMI/RFI filtration. So I'd take a look at device that also had a coax input. You might want to just check and remake all your connections and maybe put a fresh end on the incoming coax. Any chance you're also running a splitter?
     
  8. Matt^K

    Matt^K Auditioning

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    Thanks for the info Kurt, especially your past paragraph:



    That really had never occured to me, that the problem could lie within the analog inputs on the Sanyo. I tried hooking the same dvd player (Zenith DVB318) up to my roommate's Vega: there was some interference, but not the same kind I'm experiencing on my Sanyo. His TV isn't hidef (I couldn't even get the 480p working on his so I had to test this over composite), so I couldn't test higher resolutions where the interference that I'm experiencing on my Sanyo would be much more prevalent, but this has nudged me in the direction to where I'm going to try exchanging the Sanyo for a new one.

    Maybe the sanyo HT32744's components are more sensitive to interference in general (it was a ~$700 hdtv, so I guess I'm getting what I paid for!), or perhaps I'm just unlucky and purchased a set with bad analogs and an exchange will rectify this; I'm definetely hoping the latter. I need to borrow a buddy's van to transport the set (and I need to bribe some friends to help me carry the thing up two flights of stairs... carrying it down was hard enough but I shudder at the prospect of going in the reverse direction), so it'll be a week or so before I can return the thing. I will return with my results with the new set.

    Thank you both for your advice and your time.
     
  9. Matt^K

    Matt^K Auditioning

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    I don't understand Chu, I don't think I have any "coax" invloved in my system at all (unless that term also applies to the materials in the blue jeans / Ninteno component cables); I don't have cable tv hooked up to the set at all. All I have plugged in is the dvd player and the gamecube.

    I can get one digital OTA channel without any sort of antenna hooked up to the tv @ about 50% reception (I'm guessing one of the towers across the street is broadcasting the channel), maybe that lead to the confusion.
     
  10. Chu Gai

    Chu Gai Lead Actor

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    My misunderstanding. Try capping the unused coax input with aluminum foil or a shorted out rca plug.
     
  11. Leo Kerr

    Leo Kerr Screenwriter

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    Yes, I was about to suggest some sort of termination of 'open' jacks.

    I wouldn't worry too much about the cell-towers. Most cell towers radiate a peak of 10w from each antenna, generally directed.

    The radio towers, on the other hand, put out anywhere from 10 thousand to a genuine million watts of power. (Granted, megawatt transmitters aren't exactly common, but they do happen. You may be able to find out who is using those towers and for what from the FCC's web-site. That used to be available.)

    A difficulty with the mongo-towers is that while they're targetting a specific channel band, like any system, a true brick-wall filter is bad. You're getting a whole lot of broad-spectrum RF noise, and apart from maybe some added shielding of grounded lead-foil, you may not have much hope.

    What may help, except for the fact that none of your equipment supports it, would be balanced connections.

    Another thing that might possibly help (unlikely as it seems) would be to try it with a ground-lift installed. (Unground the system - just for a brief test.) You may be getting pollution through the grounds... to wit, you may also want to see about adding an independant ground from your equipment's chassies.

    Probably the most effective thing, however, would be to move.

    Leo Kerr
     
  12. ChristopherDAC

    ChristopherDAC Producer

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    Actually, I was thinking a bad ground might be to blame. Always my first thought, after a few bad experiences in Electronics lab. :b
     
  13. Matt^K

    Matt^K Auditioning

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    Thanks for the suggestion, but I'm confused (again)... I'm a complete eletronics neophyte; a ground-lift is a little adapter that plugs into a power socket and disables the ground-prong, right? Well, neither the TV, the DVD player, nor the gamecube use 3-prong plugs to begin with... all the cables just have 2-prongs. Does this mean that they are all ungrounded? (I'd imagine that is just a lawsuit waiting to happen so I'm sure my assessment is wrong.) Would the ground-lift still do anything if the power cables are two-prong (as they are in my situation)?

    Thanks for the additional suggestions and please keep them coming! If anything, I'm getting a lot of great information and background on basic electronics [​IMG]

    EDIT: Checked the FCC site, didnt see a mapping service on there but I found one at (can't post it due to my limited number of posts, but its easy to Google).

    Anyways it looks like I have 95.7 KUSS-FM on the opposing hill from me and they are broadcasting at 29,000 watts. Using their transmitter location coordinates, it seems that my initial guess was way off and they are actually about 0.573526 miles away from me.

    At a half a mile and 29,000 watts, is it still possible that the radio station is the source of the interference I'm seeing?
     
  14. Leo Kerr

    Leo Kerr Screenwriter

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    29kw at half a mile is a lot of power, even if it is an omni emitter.

    As for your components being ungrounded, well, it was worth a shot (but now that I think about it, most of my stuff is, too... projector being the exception.) What you will probably find is that each of your devices is 'polarized,' where one blade of the plug is larger than the other. In a properly wired house and a properly designed piece of equipment, this should be 'as good as' grounding it - from a safety standpoint. Not sure about interfearance rejection.

    I'm curious, though.... is this a situation where balanced/lab/technical power might help out?

    Leo Kerr
     
  15. ChristopherDAC

    ChristopherDAC Producer

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    When I was living in a dormitory, about half a mile from the college radio station, I could pick up that station very easily. My reciever has an F connector for the FM input, with a self-sealing feature [spring-loaded flap which makes it into a faraday cage when nothing is inserted]. I found that simply inserting a paper clip into the jack opened it enough to let the signal in and give me flawless reception. In fact, when I had a coax connected to it, the signal leakage at the joint, or pickup on the shield, or something, had the same effect. So yes, physically wrapping unused connectors [tho you can buy RCA short plugs at radio shack for just this purpose], possibly your cables in use, in the last extremity your whole set or even the walls in foil, should give you some relief. Of course, that last step might justify moving instead, unless you're one of these compulsive guys who wants $500 cables for his HomeTheatreinnaBox [​IMG]
     

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