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Speakers pick up radio signals

By jerkface
Sep 15, 2003
  1. I just moved into a hotel for university (our college bought a hotel and turned it into our residence) and everyone's computer speakers pick up radio signals. It didn't happen before I moved in here..

    If your computer is idle or playing music or whatever the same faint radio signal can be heard from my speakers and sub-woofer.

    Anybody have a solution to this? Someone suggested "shielding" for a similar problem but I'm not sure what that is or how to do that..

    thanks.
     
  2. Nic

    Nic TechSpot Paladin Posts: 1,928

    Well I've never heard of this problem before. I dont think your speakers are picking up the signal through the airwaves, but it is probably coming in through some other route and being amplified by your speakers.

    Do you know what station you are picking up and where it is broadcast from?
    Is it an AM waveband channel with a transmitter source nearby?
    Does the sound go away when you disconnect the speakers from your PC, but leave them powered up?

    Radio broadcasts are at very high frequencies, so if you are picking something up, it will likely be on an amplitude modulated carrier (AM waveband), which may be coming in through the mains supply circuit. I'm only guessing here, but if you can get hold of a mains filter, then give it a try. Be sure to use it with both your speaker's psu and with your PC, though I suspect the speaker's will prove the more likely culprit.
     
  3. jerkface

    jerkface TS Rookie Topic Starter

    My friend said he had the problem even when his speakers were NOT connected to the PC, but still powered up.

    I can't tell what radio station it is, It's not the best reception and i'm new to this city and it's stations...
     
  4. jerkface

    jerkface TS Rookie Topic Starter

    do you know how much would a mains filter cost and where would I could get one?

    thanks again.
     
  5. Nic

    Nic TechSpot Paladin Posts: 1,928

    Try using a mains filter on the power input of your speakers. You should really have one of these to protect your computer from power surges. That will at least allow your to check if the radio signals are being picked up by the mains wiring.

    They are pretty cheap, possibly around $30 (good one) from an electrical or computer store. See if you can borrow one first from another student.


    Belkin
     
  6. Nic

    Nic TechSpot Paladin Posts: 1,928

    Make sure you get a mains filter that has RFI filtering built-in, so that it can remove radio interference. Those Belkin filters are pretty good.
     
  7. Whyplash

    Whyplash TS Rookie

    I keep picking up radio signals on my pc speakers as well... is driving me nuts.
     
  8. StormBringer

    StormBringer TS Rookie Posts: 2,871

    a filter for line should solve the problem. Most sets of speakers come with one of these built in to the power cable(its the little cylinder that is near one end)
    You can also purchase these filters that attach to an electrical outlet, in several varieties, you may be able to get one from the power company to filter the entire line. Call and ask them about it. It isn't exactly cheap though.
     
  9. jiklo

    jiklo TS Rookie

    I had the same problem at home with my comp speakers except for that i could hear police radio !?!?!?!
     
  10. jiklo

    jiklo TS Rookie

    also my comp didnt have a seperate power source (it didnt come from the mains is what i mean)
     
  11. MrGaribaldi

    MrGaribaldi TechSpot Ambassador Posts: 2,802

    I've had the same problem, though I picked up Russian signals, and those did not come through the mains.

    From what I've gathered, it's mostly a problem with badly shielded speakers and cables. The phono-cable functions as an antenna, though I don't know what affects which frequency it'll pick up.

    Sometimes, all that is needed is that you move your speakers a bit to the right or the left (as they'll then avoid the signal), or wrap the cables in tinfoil (to check before spending money on cable shielding) to see if that helps.

    Of course, if it's el-cheap'o speakers, then it could be more cost-effective to buy better speakers than to shield the current ones.
     
     
  12. NEUtral zONE

    NEUtral zONE TS Rookie

    I doubt that filtering the mains will do the trick, although it is possible. I think the signal is most likely to be being picked up on the signal lines into the (powered) speakers. The answer is to get a ferrite ring (Tandy, Maplin) and put a few turns of the signal cable around it. The idea is to increase the cable impedance at RF frequencies so the signal is filtered. Audio will be unaffected. This is cheaper than a mains filter & I'd be inclined to try it first.
     
  13. LNCPapa

    LNCPapa TS Special Forces Posts: 4,331   +277

    I had the problem several years back with CB radio. 16 years ago I had a pair of Bose 601 + 301 comb that I could intentionally pick up CB radio with. All I had to do was turn my receiver all the way up - with no input source. If I did that I could faintly hear CB through the speakers. Also, if I picked up the telephone I could hear the CB conversations clearly. I was only 13 so I didn't try to do anything about it, but I used to show it off to my friends all the time.
     
  14. MYOB

    MYOB TS Rookie Posts: 527

    Ferrite rings. Thats what I have to use to get clear signals from the cables out of my AEI Digisender into my PC - the audio leads get interference from the PC and the Digisender itself (it uses ISM bands). Ferrite at the Digitsender end, Ferrite and the PC end. I use clip on rather than rings, as the rings are very, very brittle.
     
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