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Bose Employee
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Oct 1, 2008

Radio Interference

Dear CSD Practitioners,

I have had 3 recent instances of AM Radio interference crop up.  All involve Red Line processors (with Dante cards, not that it should matter), all 3 in completely different geographic locations (in fact, different states in the US), and all with AM Radio stations coming in on analog mic lines.  It is generally the longer cable runs - not so much the shorter cables.  This seems odd to all of the sudden get 3 in close succession (2 different contractors).

The first one that came up a couple months ago, the contractor had not run new cable and I dismissed it.  The second one was in a location within a block of an AM Radio Station transmitter and again, I blamed it on close proximity and a local condition.  The contractor added lots of filters and cleared up enough of it to be 95% masked - i.e. passable.  This last one I just now heard about is not near any known radio transmitter.     

Now I'm wondering.  I have never experienced this before with any Bose front end electronics, so I'm wondering if anyone else has run into this with the fixed I/O processors?  In a past life with non-Bose mixers and processors, I used lots of individually shielded and jacketed multi-cables with an overall shield and jacket as a preventative step.  While I only had trouble in an extremely few sites - and after exhausting all other possibilities like differences in ground potentials, bad solder connections, and the other usual suspects, finally connecting the drain wire on one end of the overall shield generally eliminated this issue.  But in these recent 3 instances - with brand new 100% foil shielded cable over 22 AWG twisted pair conductors installed, connected to new properly installed and wired wall plates, this is suddenly popping up.

Any ideas, comments, suggestions?   Is it just a bad dream?

Best regards,

Dave   

2 REPLIES 2
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Bose Employee
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Oct 27, 2017

Re: Radio Interference

Hi Dave,


Thank you for reporting this issue.
You mention that it happened only with the ESP FIXED IO.
With all versions or with one particular?

Were the systems running for a period of time, or did it happened already during commissioning?

I can recall one church project were they had AM  interference and it turned out to be an incorrect grounding in the 19" rack.

BR
Arno

PS I will send you a private message to discuss something else.

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Bose Employee
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Oct 1, 2008

Re: Radio Interference

Thanks, Arno. 

All of these situations were from the initial installation.  During commissioning, I tried putting some "Band-Aids" to get by, but even extremely tight feed-forward gates could not prevent radio signals bleeding through when someone is speaking into a mic and opening the gate.  The RFI was too loud to be unnoticeable.

Here are the ESPs and a few details (all of them churches): 

1) ESP 1240 with Dante -feeding 2xMSA12X 2 meter arrays for L & R mains, 2xMSA12X single arrays for L & R delays, and a single MSA12X regional monitor.

2) ESP1600 and ESP1240 - both with Dante handing audio back and forth between them.  2 PM amplifiers with ESPLink.  RFI on several inputs within both ESPs (not just one of them).

3) Two ESP1600s and one ESP1240 - all with Dante handing audio back and forth between them.  2 PM amplifiers with ESPLink.  RFI on mic inputs within all 3 ESPs.

4) I just remembered another situation in yet another US State with a 3rd contractor.  This involved a small amount of radio and an unacceptable level of background "hash" (static like random white noise) coming from both WP22B-D endpoints (one within 20 feet of the rack and one 150 feet from the rack) feeding an ESP1240.  This installation had 3xMSA-12X arrays left and right mounted low enough to use a flat floor optimized pattern - and obviously, an impressive amount of throw when it came to desirable and undesirable audio artifacts.  I originally blamed the  WP22B-D endpoints, but now I'm starting to wonder.  We replaced one WP22B-D with analog wiring, the other I gain staged and processed to get the noise passable (although the contractor planned to swap it out for another Bose endpoint).

If you have any tips, tricks, techniques (beyond adding caps, home-crafted LPFs or adding something like the Shure RFI chokes (which is what we're doing on a couple of them) I'm all ears (so to speak).  😉

Best regards,

Dave