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Author Topic: Cell Phone Tower Antenna Interference  (Read 7852 times)

Keith Broughton

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Re: Cell Phone Tower Antenna Interference
« Reply #10 on: May 22, 2017, 03:47:24 pm »

I missed that one but it really could depending on what power level is coming off that tower.

It could honestly be induced onto the speaker cables coming from the amp or the XLR cables going to the amp (common mode rejection either works or it doesn't, if the noise is greater than the CMRR it will be there at full volume unattenuated)


So to my question  of how  the equipment and system are being tested to determine exactly where the signal is getting in.
Without disconnecting each piece of gear and performing an isolated test, the solution may be elusive.
It seems unlikely, (but not impossible) that EVERY piece of gear is allowing this signal in.
A problem like this needs a detailed and comprehensive trouble shooting.
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Jean-Pierre Coetzee

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Re: Cell Phone Tower Antenna Interference
« Reply #11 on: May 22, 2017, 03:52:20 pm »

So to my question  of how  the equipment and system are being tested to determine exactly where the signal is getting in.
Without disconnecting each piece of gear and performing an isolated test, the solution may be elusive.
It seems unlikely, (but not impossible) that EVERY piece of gear is allowing this signal in.
A problem like this needs a detailed and comprehensive trouble shooting.

100% agree with you. He seems to be testing with headphones into the specific units as well as the amp being unterminated at the input stage and that is giving the issue still.

I would like to see if the problem goes away with the ground being lifted or with the input to the amp being terminated with a 100ohm resistor between pins 2 and 3.

I don't see any extremely high level gear there hence why I said I'm not sure of the RF shielding in the crest amp and the 02r, I'm assuming it's non-existent for the CD player and I also addressed the mics and mic cables possibility.

He needs more in-depth analysis and might not even have the tools at his disposal to test everything. A good RF spectrum analyzer will tell him immediately if the problem is with the wireless coming off the towers or if it is something else.
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Shad Groverland

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Re: Cell Phone Tower Antenna Interference
« Reply #12 on: May 22, 2017, 03:53:31 pm »

I missed that one but it really could depending on what power level is coming off that tower.

It could honestly be induced onto the speaker cables coming from the amp or the XLR cables going to the amp (common mode rejection either works or it doesn't, if the noise is greater than the CMRR it will be there at full volume unattenuated)

What shielding is on your XLR cables, a proper braided shield or simply one of these wrap around kind of things or is it a foil shield with a drain wire.

Considering what you are describing the problem could even be on the actual system ground or being induced onto any ground cable. This might be a dangerous suggestion and don't try it if you feel unsafe and definitely don't keep it that way but lift the ground to each device individually and then all at once to see if it solves your problem, I re-iterate this is a testing measure and you should not leave it that way you simply want to find the problem.

Give us as much information as you have, what model and brand of mics, brand of mic cables, brand of connectors. Your using an 02r and I'm not sure how the RF isolation is on them, likewise with the crest amps.

If has happened a few times at our national broadcaster where a correctly wired XLR cable just so happens to have to exact correct characteristics to pickup a radio station being broadcasted there louder than the mic it is attached to, never underestimate the power of an RF signal.
SHURE ULXS, Senn ew100 g2 is what I know of hand but don't have other info in front of me today. Initially tried all different kinds of XLR with no benefit and when I raised the interference is there even when no XLR is plugged in, I figured the problem is beyond cabling. Ground lifting and running new chassis grounds has been tried as well with little to no improvement. I agree that the RF or radiation coming off the cell antennas is just over powering all the internal circuitry/wiring.

Sent from my SPH-L520 using Tapatalk

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Keith Broughton

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Re: Cell Phone Tower Antenna Interference
« Reply #13 on: May 22, 2017, 03:59:22 pm »

the interference is there even when no XLR is plugged in,
How did you determine this?
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Jean-Pierre Coetzee

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Re: Cell Phone Tower Antenna Interference
« Reply #14 on: May 22, 2017, 04:00:19 pm »

SHURE ULXS, Senn ew100 g2 is what I know of hand but don't have other info in front of me today. Initially tried all different kinds of XLR with no benefit and when I raised the interference is there even when no XLR is plugged in, I figured the problem is beyond cabling. Ground lifting and running new chassis grounds has been tried as well with little to no improvement. I agree that the RF or radiation coming off the cell antennas is just over powering all the internal circuitry/wiring.

Sent from my SPH-L520 using Tapatalk

Have you got a reliable connection to ground(has it been tested by a qualified electrician)? The chassis can only absorb RF if it goes to ground, if it's simply floating the chassis won't act as an RF shield from what I can imagine.

Maybe run an isolated ground out the window to a ground rod in wet ground to test for potential bonding issues in the building.

The ULXs aren't terrible quality units neither are the G2s so I doubt there's a problem there. I would check that the grounding connectors are actually bonded to a real ground source and not just to the neutral(thats what you guys do in the states right? need someone who knows the NEC to help out on this one).
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Shad Groverland

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Re: Cell Phone Tower Antenna Interference
« Reply #15 on: May 22, 2017, 04:05:30 pm »

Have you got a reliable connection to ground(has it been tested by a qualified electrician)? The chassis can only absorb RF if it goes to ground, if it's simply floating the chassis won't act as an RF shield from what I can imagine.

Maybe run an isolated ground out the window to a ground rod in wet ground to test for potential bonding issues in the building.

The ULXs aren't terrible quality units neither are the G2s so I doubt there's a problem there. I would check that the grounding connectors are actually bonded to a real ground source and not just to the neutral(thats what you guys do in the states right? need someone who knows the NEC to help out on this one).
Great suggestion, I will try that.

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Keith Broughton

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Re: Cell Phone Tower Antenna Interference
« Reply #16 on: May 22, 2017, 04:09:43 pm »

Have you got a reliable connection to ground(has it been tested by a qualified electrician)? The chassis can only absorb RF if it goes to ground, if it's simply floating the chassis won't act as an RF shield from what I can imagine.

Maybe run an isolated ground out the window to a ground rod in wet ground to test for potential bonding issues in the building.

The ULXs aren't terrible quality units neither are the G2s so I doubt there's a problem there. I would check that the grounding connectors are actually bonded to a real ground source and not just to the neutral(thats what you guys do in the states right? need someone who knows the NEC to help out on this one).
This would be along the lines of the isolated ground system as used in hospitals. The receptacle ground pin is connected back to a common ground source.
A cold water pipe that is coming into the building might also prove to be an effective ground as long as it's all metal and no PVC.
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Shad Groverland

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Re: Cell Phone Tower Antenna Interference
« Reply #17 on: May 22, 2017, 04:10:06 pm »

How did you determine this?
Unterminated, which from my experience at least tells me it is not a cabling issue. Is that not a safe concussion?

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Keith Broughton

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Re: Cell Phone Tower Antenna Interference
« Reply #18 on: May 22, 2017, 04:16:00 pm »

Unterminated, which from my experience at least tells me it is not a cabling issue. Is that not a safe concussion?

Sent from my SPH-L520 using Tapatalk
The question was how do you know the equipment is getting the noise with nothing connected to it?
How do you hear the noise?
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Jean-Pierre Coetzee

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Re: Cell Phone Tower Antenna Interference
« Reply #19 on: May 22, 2017, 04:19:09 pm »

This would be along the lines of the isolated ground system as used in hospitals. The receptacle ground pin is connected back to a common ground source.
A cold water pipe that is coming into the building might also prove to be an effective ground as long as it's all metal and no PVC.

It could be that it was metal and a section got replace with PVC underground and nobody noticed. There are 100 reasons why the ground could be compromised but it should be tested.

I wouldn't go so far as to run a dedicated ground for the technical system, I would just do this to make sure that the path to ground isn't compromised and there is just a massive floating voltage on the ground.

Maybe check for any outlets that have ground and neutral reversed/don't have an actual ground conductor but have a grounded connector(bootleg grounds).
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ProSoundWeb Community

Re: Cell Phone Tower Antenna Interference
« Reply #19 on: May 22, 2017, 04:19:09 pm »


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