10-4 Good Buddy!!

November 19, 2006 4:56 PM

Why can I hear people talking on CB radios through my computer speakers??

Either my speakers are channeling truckers on CB radios or I'm hearing voices. A couple of times a month, I can hear truckers on CB radios coming through my compter speakers. I know it's truckers out on the interstate, cause they're using that 'trucker' jargon. Sometimes it comes through clearer than others, and I have to crank up the volume to really hear it - but it's THERE.

Assuming that my speakers aren't possessed, and also assuming that I'm not losing my mind... how is this possible?

posted by matty to computers & internet (16 comments total)

You have powered speakers with amplifiers built in, right? What's happening is that the audio cables you're using to feed your signal to the speakers are acting like antennas. CB is AM, and it takes almost nothing to receive AM if the signal is strong enough. (Especially if the trucker is using an illegal power booster and exceeding the FCC regs for transmit power, which some of them do.)

The best way to prevent this is to use coax or otherwise shielded cables. Go somewhere like Radio Shack or Best Buy and tell someone there about your problem, and they'll sell you an audio cable that costs four times what a simple one costs, but which will prevent this from happening.
posted by Steven C. Den Beste at 5:05 PM on November 19, 2006

For the same reason I used to pick up AM stations on my guitar amp.
posted by DieHipsterDie at 5:14 PM on November 19, 2006

Throw away those shitty speakers you're using and get a better set. I had a similar problem a long time ago, and once I canned the $9.99 "Labtec" speakers I bought at some computer swap meet the problem went away.

Senor Den Beste summed it up well.
posted by drstein at 5:26 PM on November 19, 2006

Does any of this explain why I often get air traffic control on certain channels on my television?
posted by jacquilynne at 5:32 PM on November 19, 2006

Do you have a CRT monitor (basically, not an LCD screen). Sometimes putting your speakers too close to a CRT monitor can amplify noise (in this case, CB radio). If you do have a CRT, try moving your speakers away from the monitor and see if it helps.

Otherwise, get better quality speakers if this bothers you.
posted by dobie at 5:34 PM on November 19, 2006

For the same reason I used to pick up AM stations on my guitar amp.

I had a similar problem when I lived next to a church. They used radio mikes.

Every sunday morning, if i held my guitar at a certain angle, I could get it to say mass.
posted by Robot Rowboat at 5:34 PM on November 19, 2006

Every sunday morning, if i held my guitar at a certain angle, I could get it to say mass.

Wow, take that, Peter Frampton!
posted by blenderfish at 5:52 PM on November 19, 2006 [3 favorites]

@jacquilynne: Yes, that's also why you get air-traffic control. Like CB radios, aircraft use AM, so you can hear the signal out of a very simple receiver.

@matty: If you want to make shielded speaker cables, something like Belden 8451 would be good for small speakers. You can buy it in bulk for about $0.18/ft and then solder RCA or minijacks onto the ends (you might want to read here for info on how to prevent buzzing problems that might result). I am a little afraid of what would happen if you went into Radio Shack and just asked for "shielded speaker cables." There is a lot of snake oil out there, and you can pay a lot of money and not get anything worth buying, unless you're careful.
posted by Kadin2048 at 5:52 PM on November 19, 2006

Shielding is a good option, but it shouldn't be your first one. Instead, try this first: Install a few ferrite beads on every piece of wire coming off your speakers, the speaker leads, the power supply cord, and, if your speakers have it, the wire connecting the 2 speakers to each other. That will help prevent the stray RF from being rectified in the amplifier built into your speakers.

You can get split ferrite beads at most Radio Shack stores. Most computer monitors and keyboards have integrated ferrites molded into the cable these days, but for some reason, speakers don't.

Ham radio operators deal with this issue all the time - here's a page that addresses some other RFI-suppression techniques: http://www.dxzone.com/cgi-bin/dir/jump2.cgi?ID=10861
posted by deadmessenger at 6:08 PM on November 19, 2006

oh, one more thing: Your profile says you're in No. VA. You may want to call the Ham Radio Outlet store in Woodbridge: http://www.hamradio.com/web/stores/woodbrid.html

I've found that HRO stores are staffed by some pretty knowledgeable radio hobbyists. If you explain to them what you're seeing, chances are pretty good that the person you're talking to will be able to make a far better recommendation than anyone here.
posted by deadmessenger at 6:13 PM on November 19, 2006

Thanks for the info folks!

After reading everything here, I think the issue must be crappy cables. I have a great 5.1 surround system hooked up, but the cables that came with it are probably nothing special. Also, I use an LG Flat Panel wide-screen monitor, so CRT screens aren't a factor.

I'll try the ferrite beads before replacing the cables...

Thanks again!.
posted by matty at 6:32 PM on November 19, 2006

The wire has to loop around and through the center of the ferrite bead twice. If it just goes through once it doesn't do any good.
posted by Steven C. Den Beste at 7:11 PM on November 19, 2006

Does any of this explain why I often get air traffic control on certain channels on my television?

Yep, although the fix for TV interference is typically a little different. Air Traffic Control frequencies (108-138MHz) are in between the frequencies for US broadcast TV channels 6 and 7 (along with the FM broadcast band, the most widely used ham radio band, and a few other things.) If you're seeing interference, chances are it's going to show up on one of those 2 channels.

Assuming you have cable, you may want to call your cable provider for help with this issue, although it may take some nagging to get to someone with enough clue to figure out what's going on.

However, the simplest thing to check is the coax going to your cable box from the wall, and the coax going to the TV from the cable box. The cable should be RG6, and not RG59. RG59 is an older standard, and may not work well on many newer cable systems.

Also, make sure that there aren't any obvious cuts in the shielding of the cable, and that the coax connections are wrench-tight - you should NOT be able to remove your cable connectors by hand.
posted by deadmessenger at 8:33 PM on November 19, 2006

The wire has to loop around and through the center of the ferrite bead twice. If it just goes through once it doesn't do any good.

Correct - to be effective, the wire has to make at least one full 360 degree turn around the inside and outside of the bead. If you can spare the length, and your ferrite has a big enough "hole", you may want to add extra turns - there's a diminishing return there, but it doesn't hurt.

Here is a picture of a properly-installed ferrite bead.
posted by deadmessenger at 8:40 PM on November 19, 2006

Does any of this explain why I often get air traffic control on certain channels on my television?

Yes. Aviation radio is also AM (amplitude modulated).
posted by neuron at 9:25 PM on November 19, 2006

This used to happen on my wireless headphones, and I picked up a cell phone conversation more than once which surprised me because I thought cell phones were a little more secure than simple old radio.

There are some good answers here already so I'll just support getting better/shielded wires.
posted by bangitliketmac at 10:36 PM on November 19, 2006