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cellphone interference
I run a live set up (City Council Meetings) with 16 mics.. that are always open. I get intereference from some cell phones especially nextel what can I do (besides turn off the cell phones) to stop a cell phone signal or frequency from interfering with my audio signal?
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4 Replies
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[Legend] “I get intereference from some cell phones especially nextel what can I do (besides turn off the cell phones)…”
OFF is the best way.
The frequent “polling” (with the tower) a powered-up cellphone does (even when not in use) can a noisey problem when it sits in close proximity to A/V gear.
Alternative:
If some of those at the mics “need” to keep their phones ON…Assign a “cellphone officer” who collects those phones before the meeting, sits far enough away from the cables and gear that the RF noise does not get amplified, and answers any phones that might ring during the meeting. That Cell-officer would have instructions from each member as to what constitutes an “interruptible” call and whould hand the phone back to that person at that time.
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I didn’t talk about and “RF Choke” that might help a bit.
You’d affix a capacitor across the conductors of each mic cable just as each cable came into the mixer.
The right value cap might reduce the RF signal while allowing the voice audio frequencies to pass.
The PROBLEM with this is that it will not be 100% effective as the RF will have harmonics that are at the same frequencies that you need to amplify.
Shutting off the phones (or the “officer” idea) will work more effectively.
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GSM issue only, so there’s a good way to discriminate against Cingular users. This is actually a pretty big issue; it even interferes with hearing aids. I wonder if the FCC spent much time looking at that before hand, or they just spend all their time watching the superbowl over and over 😉
Vince
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You might look at a company called Clock Audio. They make a line of microphones that they call “RF Friendly” we are currently trying out a couple of their mics for use in a similar situation as yours.
Good luck
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