Radio interference

[Warkitty]

Here's an interesting question from my tenants. The house is right below a radio tower broadcasting for 103.7. She's having some interference problems. Apparently, she's picking up the signal on her computer speakers. No big deal maybe, but the real problem is "The problem is the six 20-ft. mic cables, attached to the five Shure SM-57 mics and one Shure WD20 mic, and to a lesser degree, the two instrument cables, patched into the Behringer XENYX 2442 mixer, produce an audible signal of KISS-FM 103.7" With the mixer plugged in and headphones plugged into the mixer she's picking up 103.7 quite clearly and as a result can't perform live streaming into Second Life (and yes, comments could be made about that, but let's not).

The question. Can this be gotten around, if so how? With all the radio types on here, surely someone can help?

[daworm]

Any length of wire is an antenna, to some degree or another. Shielded cables with proper grounding may help (with older houses, it is common for there to be no third wire ground, even if you have three prong outlets), but it may not be enough. It looks like that mixer uses 1/4" jacks and not XLR balanced inputs, which probably doesn't help, as the balanced inputs would both pick up the radio signal equally, which would cancel out at the input. A standard 1/4" jack has a ground and signal wire, and if there is no good ground, then the signal wire will pick up the radio signal, but not have anything to cancel it out.

I'm not all that great with analog stuff, but this is fairly basic electronics stuff.

[mandrake]

Shorter mic cables would help, if the third pin ground cannot be verified good, then a wire attached to the mixer's case and attached to a cold water pipe might be enough to kill the interference. Make certain everything with a line cord still has all 3 pins, a common audio person's trick to eliminate ground loops is to cut a ground pin off, rather than to find what is really wrong and fix that.

Reminds me of a medical equipment service call several years back. I had gone to Jamestown, Tn to check out a treadmill system and I noticed the recorder styli were buzzing. I started paying more attention and started hearing music and then an announcer. He eventually gave the station's call sign. About then I recalled seeing a tower as I drove to the clinic, stepped to the back door and opened it ... yep , there it was, the local radio station, call sign I had just heard painted in big red letters, right in their back door.

[Bryan Stone]

all I know how to do is book segments, show prep, run a board & turn mics off & on, a throw away comment here & there, try and compete with & please egomaniacs, & how to get fired from morning radio shows.

so I'm really no help on this.

[Tsavodiner]

At least you admit you're good at it.

[Bob]

Go to the laundry room or some where that you can easily check the circuit is grounded. Run a 3 prong drop cord from there to the mixer and see if it sounds better.

[Warkitty]

She say's per the specs, the mixer does have XLR balanced input.

[duke]

Mar 23, 2010 6:52:57 GMT -5 Warkitty said:

She say's per the specs, the mixer does have XLR balanced input.

A great start, but apparently not sufficient to cure the problem.

daworm gave some great advice. Most of the long cables should be constructed with shielding already, but only opening up the connectors will verify.

With the extensive use of plastic in many plumbing installations, even a cold water pipe is no guarantee that a good ground is present, but an easy place to start.
The best ground is at the metal stake in the ground below the electric power meter. All other grounds should tie back to that stake. Many do not or of of such small wire as to be ineffective.

She may need someone with a good VOM and a good understanding of the principals involved to check the installation.

The radio station my be willing to send one of their techs to help.

[daworm]

She say's per the specs, the mixer does have XLR balanced input.

Is she using them (they are the three pin connectors on top) or the 1/4" jacks below them?

I agree with duke, the radio station may send someone to help. FCC regulations cover both the station and the mixer manufacturer as to causing/accepting interference.

[Warkitty]

The radio station hasn't returned her calls.

[duke]

Filing a Complaint with the FCC

If you cannot locate the source of the interference and the problem continues, you can file a complaint with the Federal Communications Commission (FCC), which has established rules to reduce interference. There is no charge for filing a complaint. You can file your complaint using an on-line complaint form found at esupport.fcc.gov/complaints.htm. You can also file your complaint with the FCC’s Consumer Center by e-mailing [e-mail]; calling 1-888-CALL- FCC (1-888-225-5322) voice or 1-888-TELL-FCC (1-888-835-5322) TTY; faxing 1-866-418-0232; or writing to:

Federal Communications Commission
Consumer & Governmental Affairs Bureau
Consumer Inquiries and Complaints Division
445 12th Street, S.W.
Washington, DC 20554.

What to Include in Your Complaint

The best way to provide all the information the FCC needs to process your complaint is to complete fully the on-line complaint form. When you open the on-line complaint form, you will be asked a series of questions that will take you to the particular section of the form you need to complete. If you do not use the on-line complaint form, your complaint, at a minimum, should indicate:

*

your name, address, e-mail address, and phone number where you can be reached;
*

the type of company you are complaining about (telephone, wireless, Internet access provider, TV or radio station, cable or satellite provider); and
*

any additional details of your complaint, including time, date, and nature of the conduct or activity you are complaining about and identifying information for any companies, organizations, or individuals involved.
www.fcc.gov/cib/consumerfacts/interference.html

[Bob]

call me silly but wouldn't it be easier to verify the plug that is powering the amp is grounded? and perhaps that the mic cords are XLR?

[Warkitty]

Yes Bob, I think it would be:D

[mandrake]

Try this if the unit is properly grounded. Unplug all of the inputs, then listen to the mixer's output.
(Speaking of which, is the mixer's output goung to a computer's sound card input? That's what I read into your description.) If everything is quiet, you likely have an open shield on one of the cables. Locate that by plugging in each cable and listening. When the radio signals resume, you have the bad input device, cable, mic, etc.

One thing to keep in mind is that the radio station is not responsible for your equipment self-rectifying their signal, which will happen to any solid state device at close range.

[Warkitty]

Thanks mandrake, I sent her your response to try.

[mandrake]

Let me know what she finds.

[mikeydokey]

Mar 22, 2010 23:02:11 GMT -5 Bryan Stone said:

all I know how to do is book segments, show prep, run a board & turn mics off & on, a throw away comment here & there, try and compete with & please egomaniacs, & how to get fired from morning radio shows.

so I'm really no help on this.

So how many egomaniacs have you pissed off Bryan? I know you've been fired a lot.