Subject:Help With Cause of Static

Posted by: Larry Clifford

Date:6/25/2012 7:12:55 AM

I have been recording meetings at our church for about 3 years. The transmitter is a Decade MS-100 low power FM transmitter. The receiver is a Cowon D2 FM recorder similar to many small mp3 type recorders. The recorder is less than 2 feet from the transmitter with no barriers.

About 2-3 weeks ago static start to be recorded over the talks. This does not occur at any other location. I have uploaded a sample file, which has been shortened from the original 2-hr file, here: http://dl.dropbox.com/u/299989/2012-06-24%20-%20Sample%20of%20Static%201.zip

I notice that before the meeting starts the static occus at about 33 second intervals. It also occurs throughout the meeting, but I have not verified if it is at the same intervals. It very likely is.

Can anyone give me any ideas whant the cause of the static might be and a possible suggestion how to eliminate the static. I know the information I have given is minimal.

Thank you for your help, Larry

Subject:RE: Help With Cause of Static

Reply by: roblesinge

Date:6/25/2012 7:38:46 AM

This sounds like radio interference to me. You said you're using an FM transmitter, any reason you can't just take a direct feed out of whatever mixing device is being used. There could be any number of things causing the interference. Since it's intermittent, my guess would be a mobile device of some kind. It's the most likely culprit, since probably everybody in the place has one, trying to share bandwidth with your FM transmission. Maybe someone else has heard this specific type of interference before and might know what it is.

Rob.

Subject:RE: Help With Cause of Static

Reply by: Larry Clifford

Date:6/25/2012 8:22:12 AM

Rob,

Thank you for the quick reply.

The transmitter was installed primarliy for the hard of hearing if they bring an FM receiver. Nobody does.

My next step is to test this today with all of the lights off in case it is a balast in a florescent light. If so, then the fun begins trying to determine which one.

If it is something in the neighborhood, then I will have no control over it.

Another option is to change the frequency. We have been using the same one since it was installed.

I don't think I will be given the option to directly plug into the sound system. That will requie some research to see what is required for the Cowon recorder.

Subject:RE: Help With Cause of Static

Reply by: rraud

Date:6/25/2012 10:58:41 AM

Since it happens at regular intervals, I'm guessing some kind of cell-phone type interference or something getting in via the input cable. I also 'sounds' like a moisture connection issue Try moving the recorder away from the transmitter, and confirm you have good 'shielded' cable and the connectors are clean and wired properly.

Subject:RE: Help With Cause of Static

Reply by: Chienworks

Date:6/25/2012 12:06:12 PM

Given all the parameters you've listed: short fixed distance, FM, MP3 recorder, no one else using the signal ... seems to me that rather than waste another moment with it i'd ditch it all and go with a wired connection to a better recorder, or even a PC. Tell the church board that a direct wired connection is the only way to get a reliable recording, will avoid all the problems you are having, and will cause no problems with the rest of the sound system at all.

If at some point you do ever have someone wanting to use the FM signal then have the transmitter and recorder both wired to the source.

Subject:RE: Help With Cause of Static

Reply by: musicvid10

Date:6/26/2012 5:42:03 PM

That's almost certainly a cell phone too close to the equipment.
It even happens in wired and new equipment.
Most common example is someone setting a cell phone on top of an instrument amp.