Radio Signals in my System.

[lieperjp]

Originally Posted by museav

...some older Mackie mixers were susceptible to RF on their inputs, for which Mackie introduced a fix that was incorporated into later models.

Do you know what model? Our church as a 15-yr old mackie console that has this problem with some of its inputs...

[museav]

I believe that it was older VLZ series models and corrected in the VLZ Pro versions. Supposedly one of the design goals of the XDR preamps was much improved RFI resistance. Mackie did offer a modification for the units that had problems, you could probably contact them and ask if it might apply to your mixer.

[Blah067]

Originally Posted by TimmyP1955

Listen to the noise on the console's headphone output. Starting with the local line level sources, disconnect console inputs until the noise goes away. If it does not, start disconnecting outputs.

+1 for this....

Although I start by muting all inputs, and if it goes away, unmute one at a time.
Start unplugging inputs until the sound goes away...
Make sure the sound is coming from all speaker outputs, this verifies its an input not at output. -What I mean is...-make sure that channel is in all auxs and mains, and if you hear it in all speakers, it's an input prob!

I agree, its probably a problem pre-preamp. So start checking inputs.

[SweetBennyFenton]

Well, I re-built the entire sound system over the summer. For a while, it seemed like I had fixed the problem by not using any of the old cable runs that were inside the wall of the theater.

Then last night during a nice performance of Endgame, we got to listen to talk radio for an hour through the house right speaker.

I swear... I'm almost at my whit's end. The next time a director asks me about it, I may just say that the theater is haunted.

(Update: I traced the problem back to the source following the steps y'all gave me. It's still not perfect, but I have been able to minimize it. Thanks everyone!)

[banjokeith]

I had a radio station coming through my system a few weeks ago and traced every cable I could find, with no results. It turned out to be the headphones on my board, or rather where I had them plugged in. The Allen & Heath GL2200 has a 1/4" jack on the rear of the board for headphones, as well as a very conveniently placed one right in the middle of the control surface. For some reason that day I decided to plug the headphones into the nice easily accessible jack and in doing so introduced a radio station into the system. I switched the headphones back to the rear, and 92.9 FM was gone.

The moral of this is that no matter how carefully you choose the cables you use, and how much money you spend on well-shielded connectors, RF will find a way, and if you do end up having to track it down be sure to try everything!

[Lightguy48]

Also keep in mind it may be a cable that is the right length to be resonant at the frequency of the radio station you're receiving, basically acting like an antenna. Adding 25 - 50' of cable or removing 25 - 50' will change the length and therefore no longer act like a receiver.

Another option is to install a ferrite or torroid choke, wrap the wire through the choke a number of times and it will help remove any RF on the line.