Why am I picking up a radio signal with my pc speakers?

Pepperpotty · Post by **Pepperpotty** » Sun Jul 10, 2011 7:56 pm

I've been sitting here tonight for a couple of hours. Not really doing anything music related. Browsing the web, cheking the forums etc. My pc speakers have been switched on and suddenly I hear a faint voice coming from them.

When I have them turned up I can definitely hear that it's a radio conversation of some sort but it's fairly muffled. I'm going to rule out taxi's as it's nearly 9pm on a Sunday night and there won't be that much chatter where I live. So my next guess is police radio. So how on earth are my wired speakers picking up police radio when they never have done before. And more importantly, how the hell do I stop it?!

It's not coming over the internet, I've tried unplugging it. And my speakers need to be connected to my pc to receive the signal. (Have tried keeping them powered on but unplugging them from my pc)

This is going to get really annoying really fast if I can't stop this! I hope it's just because there is a police car parked around the corner but it's been going on for about 40 minutes now!

Has anyone else experienced this?

X-Trade · Post by **X-Trade** » Sun Jul 10, 2011 8:16 pm

Could be analog cordless phone. If one of your neighbours got a new one for example. Sometimes that happens, I've heard it before.

No idea how to stop it though. Except for the usual suspects - avoid coils in the wire, put a ferrite ring on it, etc.

Pepperpotty · Post by **Pepperpotty** » Sun Jul 10, 2011 8:23 pm

Not unless it's a really long phone conversation consisting of several minutes of silence! I wondered if there might be a police car parked nearby chatting away. I really hope that's what it is and that this isn't going to be a permanent thing.

Giner · Post by **Giner** » Mon Jul 11, 2011 3:46 am

LOL! We had radio blast in on our PA system one night in the middle of a gig. That one was a taxi. The lyrics went like this:

. . . the waiter brought a tray
and so it was . . .
"Taxi to Hertford North station, over"

It was probably poor shielding on the speaker cables. Can't really see that being a reason on computer speakers, but could be. Depends on the quality, I suppose.

Timo · Post by **Timo** » Mon Jul 11, 2011 1:35 pm

As mentioned, check your cables, the RF (radio frequency electromagnetic radiation) shielding could be really poor.

I could do the same with one particular cable and my guitar amp. The cable was really cheap (it was bundled with the guitar). Switched it for a decent cable, and no noise.

If your speakers & soundcard support balanced connections, use balanced. That would effectively wipe out all RF noise.

Try not to use a shitty onboard (integrated onto the motherboard) soundcard on your PC, these are noisy as hell.

Post by **mikemolloyuk** » Mon Jul 11, 2011 1:38 pm

ditto the above 2 posts.

Sounds like a sheilding issue.

Pepperpotty · Post by **Pepperpotty** » Mon Jul 11, 2011 1:45 pm

Well the sounds appears to have stopped today! I can only imagine that there was a police car parked nearby broadcasting. I really hope it was just a one off. New speakers and a decent soundcard are on my list of things to buy but they always seem to be down at the bottom of my list when there are much more exciting things to purchase!

Giner · Post by **Giner** » Mon Jul 11, 2011 2:39 pm

I hear you, PP. The old saying used to go that when buying components for a stereo system, spend 2/3 of your budget on the speakers. Lot of sense in that.

Pepperpotty · Post by **Pepperpotty** » Thu Jul 14, 2011 6:18 pm

Not sure if I'm looking for something that doesn't exist here or not. But speakers aren't my forte so I need a bit of help here. Is it possible to get some monitoring speakers that I can hook up to my pc but also hook up my audio interface to them too? IE at the same time. Without having to unplug one to put the other in. If it is possible does anyone know of any particular speakers please?

madbeatzyo111 · Post by **madbeatzyo111** » Fri Aug 05, 2011 6:58 pm

Pepperpotty wrote:Not unless it's a really long phone conversation consisting of several minutes of silence! I wondered if there might be a police car parked nearby chatting away. I really hope that's what it is and that this isn't going to be a permanent thing.

This a classic case of inadvertent demodulation of RF signals. Remember that old story of your grandpa hearing AM broadcasts through his metal tooth filling? Well, he might have been just a crazy old coot, but you always believed him didn't you?

Anyway, just like with grandpa's tooth, something in your system is able to demodulate that RF signal such that you can hear the conversation. I'm guessing it's an AM signal since these are easier to accidentally demodulate. This would tend to rule out the police since they typically use FM in the 400Mhz+ spectrum, possibly with trunking which would make accidental demodulation very unlikely. Unless....do you happen to live in Hazzard County where the local sheriff always seems to be chasing an orange car? Because as far as I remember they do use AM (CB) radio as their police radio, making it very easy for the Duke boys to listen in on them. And BTW, when will these nogoodniks be caught? When will the madness end??? :angry old guy get off my lawn fist shake:

It may be tough to shield from this kind of interference since the RF can come in from anywhere, not necessarily on a wire or cable connection. You'd have to build a metal cage around your entire setup and ground it to an 8 ft copper pole in your backyard to be absolutely sure. Or you can buy better computer components; cheapie ones may be more prone to demodulate.

As for connecting both your PC and keyboard, I would recommend a small mixer.

Here's one that I've used for the past 6 years with success.
http://www.musiciansfriend.com/pro-audi ... ompression

Sam CA · Post by **Sam CA** » Mon Aug 08, 2011 11:23 pm

My experience with RF was actually worse than yours. I'm the music director of a local church in LA and every once in a while when we turned on the PA system on sunday morning, there was this strong signal picked up from a local radio station that would kind of come and go randomly. It was definitely a shielding problem.