Countryman headset interference from titanium neck implants

cjanderson

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Nov 30, 2009
Location
Central Minnesota
We have one actress who has had cervical titanium neck implants. When she wears a Countryman headset and turns her head, the mic cuts out or hisses. I have changed her mic to a lavalier but even that has some similar problems. The same mic setup performs flawlessly on other actors. Has anyone of you experienced such issues and if so, how did you solve them?
 

Aaron Becker

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Apr 27, 2016
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North Dakota
I've certainly never dealt with this, and although you say the problem only occurs when they turn their head, I have to wonder if it's actually a RF interference issue? How is the cable routed on the actress? Down the back to a pack in the bra, or is it costume mounted? How close is the cable to the implant (this may be difficult to determine, I realize).
 
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DrewE

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Mar 18, 2019
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Vermont
I wonder how close the beltpack is to the implant. The RF circuitry would be in the beltpack, and on the beltpacks that I've seen the antenna is separate from the microphone lead. The wire to the microphone oughtn't be subject to interference or cutting out due to running near metal; it's just a shielded audio cable. (Note I said oughtn't, and not categorically isn't!)

For beltpack receivers, often the cable to the headphones or whatever is the secondary antenna for a diversity receiver.
 

JD

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North Wales PA
Doesn't sound like a mic issue. Never seen it, but it could be there is something about the length of the implant that is causing a RF problem. Try moving the frequency far away from the current setting, even a different band if available.
 
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FMEng

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That's an RF issue, not a mic issue. The metal implant is only having an affect because the system is operating marginally to begin with. The root cause could be any of the basic wireless mic issues from a poorly chosen channel, an intermodulation product from other mics, to receiver antennas.

It could also be an external factor. With the TV repack and the wireless companies moving into the upper portion of the UHF band, it's possible that the RF environment in your area has changed, causing interference to that mic system. The 50 milliwatt mic transmitter might be competing with a 1 megawatt TV transmitter.
 

BCAP

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I'm not an RF expert, here are some things to try (feel free to disagree if you find any of my suggestions ridiculous)...

1). Has the whole wireless system been effectively RF coordinated? If so can you give us some more information - number and make/model units you're operating, frequency ranges, etc. and what process was used to select frequencies, if you used software or let the units find their own frequencies, etc. And frequency of the actor's pack in question.

2). Do you have a portable RF scanner? Might be good to do a sweep of the area inside your venue with all transmitters off and in different locations to identify potential conflicts. Some coordination softwares will let you import these scans as files to help coordinate the whole system around the used spectrum in and near your particular venue.

3). Don't rule out a loose antenna on the pack. Actors are tough on the packs, I've seen them pull the pack out of their pockets by the antenna (yikes). On some packs a sketchy antenna is easy to repair if you're handy with a soldering iron - have to be careful not to change the length of the antenna tho. Should be relatively easy to diagnose too. Just do a antenna wiggle test with the channel on and then twist the antenna slightly (being very gentle and careful of course). You will find out in a hurry if your pack's antenna might be the issue.

4). There are some different antennas you could try on the receiver that may help the problem if it still persists, maybe a paddle antenna might help. RF Venue has some interesting options.
 
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BCAP

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Ohio
P.S. I never had an issue exactly like you describe. I'd be really surprised if it was the actor's implant though.

Similar issues I've had came down to the microphone connection, the cable, or the installation technique.

Especially with the type of mics that have a connector inline (like a Microdot on the headpiece). The connections can loosen or with use and abuse I've had cables go bad.

Also have had issues where the cable gets pinched in the collar of the actors's costume or on some other place and essentially puts stress on the cable, it can cause clicks, pops, dropouts and it can seem like an RF issue at first.

There was one other issue I had that I never could actually confirm - the actor was wearing a suit coat with some kind of polyester shirt underneath and it was winter and very very low humidity in the theater. I believe there was static cling inside the actor's costume that interfered with either the mic or the transmitter but again I could not confirm.

Hope any of this will help you. Good luck!
 
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FMEng

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I like BCAP's idea that the antenna on the pack could be broken. That might make for more difficulty in the presence of the nearby metal.

I would experiment by first swapping systems with another actor. If the problem moves to the other actor, then I would swap frequencies to determine if it's interference, or hardware.
 

cjanderson

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Location
Central Minnesota
As I pointed out, we have tried this Countryman and this bodypack with other actors and they have performed flawlessly. Only the actress with the neck metal causes us problems. It's the neck metal for sure, but what's the solution?
 

FMEng

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Have you tried a different pack on the metalic actor? I still think there is something under performing in that particular transmitter/receiver/frequency that allows the metal to cause problems. What do you see on the receiver's RF meter with the problem transmitter turned off, and all of the other transmitters ON? How's the signal strength when it's operating?
 

FMEng

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Yes, we’ve tried different transmitter/receiver/mic combinations. She’s unmicable.
Wow, that's intriguing. I suppose the metal could be causing a great deal of RF absorption. Different wavelengths should be able to avoid the body/metal resonance. Assuming you are using the typical UHF frequencies, I would try VHF or go much higher like >900 MHz or 2.4 GHz. I know Shure offers VHF and 950 MHz in higher tier products. Their budget PGX-D would be a less expensive unit to try. Several makers have systems on 2.4 GHz.
 

FMEng

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One more though here. Does the costume have any metallic properties? I recall having trouble with a mic underneath shiny/sparkly fabric.
 

cjanderson

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Nov 30, 2009
Location
Central Minnesota
It was The Little Mermaid so many of the costumes were sparkly. Their mics were crystal clear. This character was the least sparkly of all. I wish I was a Hollywood orthopedic surgeon because this would be an article for a medical journal.