Cell phone interference in sound system

[tmooney]

Found this site through a Google search and located some very interesting posts on this subject. For the past 6 months I've been trying to narrow down unwanted interference in our church's sound system and have come up empty. The building is in the process of closing and consolidating into another church but it is still being used until mid next year.

The sound system was put in 30 years ago, nothing is balanced and the main control unit is not grounded. I have inspected all the cabling and I cannot find any breaks in the hardwired system. The wireless units are not the problem because they are rarely used and always turned off.

Yesterday was the worst, I heard the "PSWSTP" at least 10 times along with constant popping, yet 3 weeks ago I videotaped 2 services and my audio track is crystal clear. Not a pop, nothing. The problem is totally random.

What I don't understand is the proximity issue with a potentially offending phone. I have made sure that know one is carrying a phone anywhere near a microphone or near the old sound system. I can't re-create the problem with my 2 phones when the church is empty.

Is it possible for a phone to cause the interference even though it 40-50 feet away from system?

I know the obvious answer is no phones in church but it still happens.

Thanks in advance.
Tom

[waynehoskins]

Hi, welcome.

Shooting from the hip, I'm guessing the issue is not with equipment directly, but with cabling. Nothing is balanced, you say? Ancient long unbalanced lines are perfect for picking up phone interference, which of course didn't exist 30 years ago.

Another possibility, this also happens sometimes with gutiar/bass players. I'm not sure if it's single-coil pickups that are the problem or unshielded wiring in the guitar body, but once in a blue moon you'll see that happen. Before you put too much effort into hunting gremlins in the sound system wiring, you may as well try to make sure the gremlins are in fact in the sound system and not in a guitar or bass.

[tmooney]

I know it is in the main sound system that runs the microphones. We have an organ and a piano and they are run off of a seperate set of speakers and power line. We have had interference during services when the organ was shut off and I can hear it come through the main system.

At this point I would be happy just to re-create the problem on my own.

Thanks again.

[petereit]

Originally Posted by tmooney

nothing is balanced and the main control unit is not grounded.

I don't think you'll ever find satisfaction until you rectify those two fundamental problems.

[waynehoskins]

Originally Posted by petereit

I don't think you'll ever find satisfaction until you rectify those two fundamental problems.

Yep, we found the problem!

Incidentally, what is the "main control unit" that's not grounded?

[tmooney]

I wish I could just gut everything and start from scratch but with the church consolidating in June it's not worth putting the money in.

The speaker lines were put in in 1974 and some of them are buried in woodwork that was done after the fact. I don't want to touch the cabling because if I somehow break a connection I am going to have to fix it.

The main control unit, as I call it, is this monstrous rack mount that has all the audio equipment wired into it. All the speaker lines run right into the wall and theirs about 24 inches of slack so I can't move it out more than 2 feet.

What's driving me nut's is how random it is. If I show up with a videocamera it never happens. Come back the next day with 20 senior citizens in the church and it pops and cracks from beginning to end.

[petereit]

Originally Posted by tmooney

Come back the next day with 20 senior citizens in the church and it pops and cracks from beginning to end.

Ah! There's the problem. One of your senior citizens is radioactive.

[waynehoskins]

Originally Posted by tmooney

If I show up with a videocamera it never happens.

Clearly the solution is to bring the camera every week.

But on a serious note, what I'd do for the next few months is run a temporary snake around the perimeter of the room. If necessary, also run a temporary drive snake from the mixing position to the amp rack. Long-term rental, cheapies, used from Ebay, whatever works best for you. If you go with a new cheap snake, I've had good luck with EWI snakes before.

[tmooney]

This is a small church, that's why it's closing and consolidating into a much larger church a few blocks away. This building holds 450 max.

The built in system has 2 podium mics and 2 choir mics along with 2 wireless mics which none of the priests use. Their is no mixing position, they all go into an old mixer and you get what you get. When I joined the church I tweaked the balance as best I could and though it's not perfect it not bad.

The problem is that all of the wiring is buried in the structure. Whoever wired this back in the day spent a lot of time fishin cable because their is not a visible cable in the house.

I work and own a small video production company, I have a closet full of audio equipment that we don't use and I could rewire that rack in a few hours. The problem is the cabling. Their is one cable for the choir and I can't figure out how it get's from the mic to rack.

I'm not convinced that it's actually phones from inside the building. It could be an outside source that's causing it. We have a service every Monday evening and tonight it hit several times. I know everyone that's at this mass and I really doubt that anyone is texting during the service and everyone knows to turn off their cell phones.

We have large bus company 4 blocks from the church and they must have a dispatcher in the building. I wonder if their bus radios could cause the problem because they go 7 day a week.

Thanks again guys.

[FlamHappy]

I hate the sound of cel phone interference.
Brrrrrt Brrrrrt.

[Josh Scott]

You don't have someone putting their cell phone close to the rack or speakers, iPhones make great noises if you leave them on a sound board or by a speaker. Every time if goes to check your email you can hear it. It sounds very digital though, not sure if that is what your problem sounds like.

[tmooney]

Follow up. The problem has not gone away in fact it is getting worse. We have posted, announced and instructed to everyone the evils of texting and leaving cell phones on during mass.

I have realized that their are 2 different types of inference coming through the system. Since we started the anti-cell phone campaign I have noticed that some of low level pops and cracks have dissipated in fact we went through a mass and I didn't any popping or cracking.

The problem is we are still getting lot's of (PSTPST) coming through the system intermittently. We have a Monday evening service and I am 100% certain that the church is cell phone clear.

My gut feeling tells me something is coming in through the electrical system. I am going in tomorrow and to check the electrical system and see if can find anything. I am going to run the main console to a new outlet to see if it makes a difference.

What's driving me crazy is I cannot make it happen when the church is empty and I am their by myself. The church is consolidating in June and we can certainly live with it during mass for the next 6 month. I not happy that it could happen during a funeral.

Any (more) suggestions.

Thanks again
Tom