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Old October 2nd, 2005, 03:57 PM   #1
New Boot
Join Date: Oct 2005
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WMF Pro Hissing Interference / GL2

I've shot over 15 weddings so far this summer and had nothing but problems with my WMF Pro lav mic. I thought I had it figured out, but at the next wedding had the same problems, hissing and interference. So I borrowed a better mic system, Shure T1-CE trans / VP3 receiver, but the same hissing . . . until I moved the transmitter cable away from the camera. ??? I use a GL2 and I thought I was getting some feedback from the camera, so I did some testing at home today and found some strange things happening. I use brand new batteries, so that isn't the issue. And distance isn't the issue because I've had the interference from as close as 5 feet. Tell me why this happens:

1. When the cable on the transmitter is wrapped/coiled up I get hissing and popping (loss of signal). There is no antenna on the WMF transmitter, so that leads me to believe the cable acts as an antenna? Right? I usually get the groom to coil the cable up and put the transmitter in his inside jacket pocket, so I should probably clip it to his belt so the cable extends??

2. When I wrap the receiver cable around the left side of the camera, underneath the lens, and up to the input, I get interference. Not so when it's just hanging free on the right side. So is that some kind of magnetic interference from the camera??

3. I've also experienced complete loss of signal when the receiver cable is wrapped around the lens and then I touch the cable with my fingers. ??? So my body must be acting as interference??

4. I've also noticed if I change the position of the camera/receiver by even a couple of inches and that can create or eliminate interference. I didn't realize VHF was that sensitive. ???

Thanks for any help.

BTW, here's some of the work I've done. (go to highlight section)

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Old October 3rd, 2005, 04:27 PM   #2
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Ok maybe too much info there for a reply, so I'll simplify . . .

Anyone know if the Azden WMF Pro mic uses the mic cable as an antenna? I seem to be getting interference when the cable on the transmitter is all coiled up, but it seems to clear up when the cable is stretched out. Am I right here?


And does anyone have any issues with interference from camera components and wireless mics?
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Old October 3rd, 2005, 04:43 PM   #3
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Yes, Azden, like many others, place the antenna inside/use the mic cable as an antenna. You should never coil this anyway, and further, never cross the mic cable with any existing antenna, regardless of the brand.
Put the transmitter where there is the least amount or no body mass between the transmitter and the receiver, especially with lower grade wireless systems like the Azden.
If the transmitter and receiver are line-of-sight or as close to LOS as possible, then it's highly unlikely your camera could/would interfere with the signal, although it IS possible.

When you wrap wire around metal, or even around non-metal, you're creating an antenna/coil. This is why you shouldn't ever wrap cable around anything when it can be avoided, and if you DO wrap it, then keep it away from any electric or magnetic devices.
Remember building your own crystal radio set in Cub Scouts? Wrapping wire around a toilet paper tube? Similar principle.
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Old October 3rd, 2005, 05:03 PM   #4
Fred Retread
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If you must gather cable, bundle it instead of coiling it by folding a convenient length of it back on itself, then a similar length forward, then backward again, etc. Secure the bundle with a tie or rubber band.
"Nothing in the world can take the place of persistence..." - Calvin Coolidge
"My brain is wired to want to know how other things are wired." - Me
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Old October 3rd, 2005, 05:12 PM   #5
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Ahhhh (light goes on) I think I realize what happened with the interference with the better mic system . . . I had the receiver cable wrapped around the camera with the camera in between the cable and the receiver, then when I moved the cable away from the camera it moved the cable in line of sight of the receiver. Also the cable on the receiver was coiled up, so that doubled the problem.

Thanks, now I understand. I'm happy I don't have to spend another $500 on equipment.
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