We recently moved into a new house in a different part of town and now that I have our PA set up in the basement, I'm getting a couple of radio stations (not loud, but enough to be of annoyance) coming over the PA. I guess this is being picked up by the mic and keyboard cords.

Anyone have any ideas how to eliminate this rf interference? P.S. All the cords are of the right kind, kbd. cords for the kbd., mic. cords for the mics., all properly shielded, grounded, etc. Thanks.

The only things I can come up with ( off the top of my head is ).

If you have a ton of exposed pipes down there, cover them up with some insulation.

Next thing...while you might have the wires for your gear ran fine, you could be getting some issues with the electrical work running through your house.

To help trace these problem spots...plug a single mic into your mixer, put some headphones on...and "scan" the mic around the basement to find problems.

Beyond that...check all the stuff in your setup chain one by one, and experiment with placement. Also run power down there from a different breaker then you are now, just cause your grounded doesn't mean its a good ground.

There is really not much you can do. This is called spurious radiation, and is not at all uncommon. If you call the radio station, they will usually send someone out to check out the situation, and some actually have filtration kits available at no charge to correct the situation. The only reason I know about this is at one time I worked in radio as a newscaster and our station had a similar problem. The station eventually relocated their transmitter and tower to the back end of a large farm and problem was solved. Living near a radio station's tower is kinda' like living next to a freeway and complaining about the traffic noise--just not much you can do about it!

Cheers,

Gary

I have heard of people tearing out the sheetrock of one room - the studio/practice room - putting in chicken wire between the studs, and replacing the sheet rock. They also make sheets of thin lead especially for this purpose but I don't know where you find it. I would think you would have to do the ceiling too and maybe under the floor if you want to get serious. I honestly have no idea how effective this is but I remember reading that synthesist Wendy Carlos did something like this to a home studio to cut rf interference.

Try isolating the inputs to the amp to identify which one is picking up the RF. If you can narrow it to either a mike input or an instrument input, you're on your way to finding the source. You didn't mention the use of any wireless mikes, they are good sources for trouble with RFI. Make sure the amp itself is well grounded too. Good luck
Ron

I worked as a musical instrument technician for ten years and got my first amateur radio license when I was 12 years old. I know about Rf.

Don't insulate your pipes. They are supposed to be grounded. Any Rf picked up by them goes to ground. Also don't bother with the house wiring or circuit breakers. It is not originating from your wall ac.

It comes from inputs to your amp or the amp itself. All it takes is for one diode in your amp or keyboard to act as a detector for RF and you get to listen to the radio for free. The mic leads and input leads from your keyboard become the antenna. Don't bother with speaker output wires they go from the amp not into it.

Do you get radio with just the pa turned on but nothing plugged into it?

Do you get radio with just the mic plugged in?

Do you get radio with just the keyboard plugged in?

Do you get radio with the keyboard cables plugged into the amp but not plugged in on the keyboard side?

Does your keyboard volume level make the radio louder?

You need to isolate where the signal is coming from. Once you have figured that out then you can take corrective steps.

Sometimes just rerouting the input cables is enough. It may go away with changes in the atmosphere. Make sure all grounds are in excellent shape. Do not use a three to two prong adaptor on anything. Use quality shielded cables on all inputs. You could line your walls with grounded chicken wire but that is pretty extreme.

After I isolated the input source of the radio signal I would experiment shielding things with a roll of tin foil.

good luck

Tom

I remember some cases where the speaker-cables acted like HF antenna's.
Most of the time they are unshielded and long.... just like open dipoles
So removing/checking them could help.

Low-pass mains-filters block HF signals captured by the electrical wiring in your house. I purchased some of these for my neighbours at the time I operated my HAM-radio station.....and they did a good job!

So, don't focus on the inputs only because HF has many 'doors' to come in.

Roel
PA3AGX

[This message has been edited by Roel (edited 02-17-2005).]

Thank you all, gents, for your helpful suggestions. Tom Cavanaugh just about hit the nail on the head. It's coming from the L/Mono output of my harmonizer which is powered by a "12vDC mains adaptor". So, short of buying a harmonizer powered direct from the mains, I guess I'm stuck with rf for the time being.

There are no radio station transmitters in the immediate area, the nearest being about 8 miles away. I suppose that's close enough, though.

Thanks again for your help, guys.

I dont know if this will help but look at this http://www.sjgreatdeals.com/kl1.html

Phil

Beyond that...check all the stuff in your setup chain one by one

Echo echo echo :P