So my first night in my new place, I’m laying in my bed, and I hear this faint music. I figure it’s from the floor upstairs, and so I disregard it. I get up in the morning, the music’s still there. After a brief investigation, I find that it’s coming from my computer speakers. Nothing was playing music on the computer. In fact, I unplugged the speakers from the computer, and I was still getting the music. Then I hear the call signs for a local radio station, 107.1. Their transmitter is a couple blocks away from my place, I think.
So… what’s going on here? How can my speakers get radio signals? Hmm?
I’m visiting the 'rents now, and experiencing the same thing with the speakers on Mom’s computer. WBFO, at 88.7, fills the background silence. On all the radios in the house, excepting a high end stereo, WBFO can be heard where there would normally be gaps on the FM dial.
If the transmitter is close to you the signal is strong. Any piece of wire laying around will act as an antenna. Somewhere in the computer speaker section there could be some circuitry that changes the FM to an AM signal. Any circuit that has an output that varies in amplitude with frequency changes will do that. After you have AM, any non-linear element, and there are lots of them around, will detect it and, voila!, you hear it in your speakers.
Call the station and explain you problem to their technical guys. They can probably give you some tips about getting rid of it.
That had me chuckling. TechGuy: “Sir, we suggest you fashion a foil plate from Jiffy-Pop - the kind with more butter but less salt - and that will deflect 107.1’s signals.”
Heh heh, I’m skeptical. The OP has computer speakers driven by radio waves? Even disconnected from the computer?
jbird3000 - tour the country with your 107.1 speakers!
Actually, any FM signal also has a certain amount of AM. All you need is enough transmit power and an antenna and you’re good to go. Didn’t you say the tower was just a few blocks away? Think 50,000 watts and be very afraid (of AM signals.)
More than likely, you’ve got a poorly soldered connection somewhere in the amplifier for the computer speakers. A poorly soldered connection can act as a rectifier, and do the job of the “detector” in an AM radio.
Possible solutions to your problem:
Plug your speakers back into your PC, and ground the metal case of the PC.
Clamp a ferrite bead around the speaker cables, preferably with a couple loops of cable through the bead.
Try a different set of speakers.
Open your speakers and resolder all connections.
There are some solutions, but they may not work on your speakers. The best fix is to use shielded speaker wire. But many computer sound systems have hard-wired speaker wires that can’t be replaced.
The station may be able to help, in fact they have an obligation to be sure their transmitter is operating with certain parameters. So give them a call and seak to the engineer.
The frequency modulators are not perfect. The modulator puts out a signal that varies just a tad in its level depending on the frequency. It is only a few percent of the nominal level, but it is readily detectable - especially under the conditions described in the OP.
David Simmons had also explained how strong FM signals can go AM. IANAEE (Electrical Engineer) so I’ll step back, counfounded on broadcast signals that can leak enough energy to move speaker coils.
Dear Lord, the temptation for tin foil helmet jokes in this thread is almost more then I can handle! I believe what you have here is a very imprecise crystal set. A crystal set is a basically an antenna assembly that lets you pick up radio signals with out power, Radio shack sold kits when I was a kid. this page here has the recipe for a basic “oat meal box crystal set” which you can build all by yourself, if you ever get seriously bored. Check out the home page as well - lots of interesting (though perhaps totally useless) home radio information can be found on this site, as well as alink to my personal favorite [Bizarre Stuff You Can Make In Your Kitchen](http:// freeweb.pdq.net/headstrong/default.htm#where), for those seldom Saturday nights when you have no date.
The most expensive “crystal radio” like this I ever saw was a telephone voice encryption unit that picked up a local AM station - but only during international calls to the manufacturer when we were testing the damned thing. It only cost a few thousand bucks, and we always checked out new equipment before delivering it to the customer. Real damned fun. We ended up sending the freaking piece of junk back to be replaced.
I started a thread about this a couple weeks ago–except my speakers don’t pick up FM radio, they pick up audio transmissions from helicopters as they fly overhead. Tin foil jokes be damned, it’s true. Every time I hear a whup-whup-whup, sure enough, a few seconds later, the speakers start picking up its communications. It used to scare the bejeesus out of me, now it’s a way of life.
Lemme clear up a couple things… The speakers have power when this happens. They’re just not getting any input from the computer. Also, it’s not a hella powerful radio station. Transmits only 50km away, I believe. And it’s not this big whopping tower either. I’ve never even seen it, but the station hq is what’s a couple blocks away. and all things lead me to believe the transmittor is there too.
I really don’t mind it. It’s incredibly faint… And it doesn’t happen all the time. It happened the first night I was here, when the speakers were in the bedroom, and a couple nights ago too. I just wanted an explanation
How about getting TV audio on my alarm radio? My girlfriend says my place is haunted.
I have this problem too, I get a local sports talk radio show and sometimes ESPN radio through my computer speakers. Since I like the stations I don’t really mind it, except that it is just lound enough to be distracting sometimes. The computer doesn’t need to be turned on, as long as the speaker power supply is on, I’ll get the interference.
I never had this problem til I went to a fiber optic hook up. The solution to your problem is simple and requires nothing more than repositioning your speaker wires. Just jiggle em around, the interference will eventually stop. When you find the magic position, be careful not to move around your speakers.
My speakers had three wires, one for power, one to connect them, and one for audio out. One of Viginia Tech’s big honkin’ radio antennas is clearly visible sitting atop the dorm next to mine. I had major radio problems. Now, I just use earphones.
