# Wireless microphone cell phone interference fixes



## Ech725 (Aug 15, 2013)

I've used a wireless lav mic in a 25'x50' lecture hall that is hooked up to a 12 channel Mackie mixer. I've noticed that every time I've used it the pas couple of times there has been an annoying pulsing noise. I believe that it is cell phone interference. The wireless mic is a lower end model $200. I've never had issues any issues with wired mics or a different handheld wireless mic. Are there any solutions to avoiding the interference? I was looking into buying a new wireless combo handheld/ lav but my budget would probably be $600.


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## 0HZ (Aug 15, 2013)

Have you isolated the interference to the stage, mix position? If it is either of those just tell people to turn their cells off. Presenters are horrible at saying they will turn it off before the start and then not doing such.


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## themuzicman (Aug 15, 2013)

What you are describing sounds a little bit like GSM noise -- does it sound like this? Cingular GSM Speaker Interference - YouTube


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## FMEng (Aug 16, 2013)

GSM phones are notorious for getting in mics. People don't realize that a cell phone periodically transmits any time it is turned on. The RF can get into any audio gear within a few inches, but condenser mics are particularly susceptible, especially lav mics. The worst scenario is a phone in a pocket next to the mic, mic cable or beltpack.

ATT and T-Mobile are GSM networks. Verizon and Sprint use CDMA which does not cause interference into audio equipment. The modulation scheme used by GSM is what makes it prone to causing problems.


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## Ech725 (Aug 16, 2013)

I checked out the YouTube video and that is the exact sound. Relating it to a stage, the mixer is backstage left and the presenter is typically center stage or stage right. It's actually a horrible set up because I have to mix from a horrible spot. I wish the mixer could be in the house or at least in front of the presenter. So would everyone in the room with a GSM have to turn off their cell phones? Or just the presenter?

Presenters walk around the room and aisle, so I imagine other cell phone signals would affect the mic. Would a higher quality mic help?

Talks for the helpl


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## themuzicman (Aug 16, 2013)

Ech725 said:


> I checked out the YouTube video and that is the exact sound. Relating it to a stage, the mixer is backstage left and the presenter is typically center stage or stage right. It's actually a horrible set up because I have to mix from a horrible spot. I wish the mixer could be in the house or at least in front of the presenter. So would everyone in the room with a GSM have to turn off their cell phones? Or just the presenter?
> 
> Presenters walk around the room and aisle, so I imagine other cell phone signals would affect the mic. Would a higher quality mic help?
> 
> Talks for the helpl



It has nothing to do with the mic quality, just make sure your cell phone is a foot or two from the console, and a foot or two from the mic transmitters and receivers. Something there isn't shielded and its inducing signal from the cell. I really only get it bad with pro gear when my cell is directly on top of an analog desk.

My money is that it's coming from the mixer


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## FMEng (Aug 16, 2013)

Don't worry about phones in the house. The interference is from a phone less than 12 inches of an audio component. Have the presenter turn theirs off. Don't lay one on or next to the console or audio equipment rack, either. 

Some people assume you want them to turn off the ringer. Make sure they understand you need the phone powered OFF.


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## Ech725 (Aug 16, 2013)

themuzicman said:


> It has nothing to do with the mic quality, just make sure your cell phone is a foot or two from the console, and a foot or two from the mic transmitters and receivers. Something there isn't shielded and its inducing signal from the cell. I really only get it bad with pro gear when my cell is directly on top of an analog desk.
> 
> My money is that it's coming from the mixer




I'm not sure who set the whole system up. The rack has a mackie mixer that is connected to an eq and amp that is connected to some small JBL speakers hardwired to the walls. 

The only other input is a desktop pc. It doubles as a classroom and conference room. It drives me nuts because multiple people have access to it so things get changed a lot. So you believe the mixer may have a connection that is not shielded? The pc connects with a 1/4" to RCA that connects to an adapter that goes into one of the channel inputs. Could that be the problem?


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## themuzicman (Aug 16, 2013)

Ech725 said:


> The pc connects with a 1/4" to RCA that connects to an adapter that goes into one of the channel inputs. Could that be the problem?



No, it is physically THE mixer. Cheap products (heck, I've inducted GSM noise into 64 channel A+H consoles) often have components in them that aren't shielded. Something inside the thing is inducting it and throwing the noise into the system.


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## FMEng (Aug 16, 2013)

Cheap has little to do with it. It is simply difficult and very expensive to keep RF of that level and frequency totally out of audio electronics. Shielding and filtering is only so effective.


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