[BC] RF interference problem

[Mike McCarthy]

I don't recall Jim ever having suggested bonding pin 1 to chassis of each 
piece of equipment in all conditions.  However, the audio common (pin 1) 
and the chassis should have jumper included to connect the two if 
necessary.  Much like the Orban 8100/9100 series processors and Crown amps.

Otherwise, Jim's rules on grounding , audio common, and bonding the two 
together are quite...sound.

MM

At 07:59 PM 1/22/2006 -0500, RLO2L at aol.com wrote
>
>In a message dated 1/22/2006 1:54:03 P.M. Central Standard Time,
>jjohnson at goodnews.net writes:
>
>Ah, hah!  Very interesting theory! One of X-Star's station's studio (an FM)
>is at  the foot of the tower. RF field strength was down where it should
>have  been, but Jay had a terrible time with RF into the air console. He
>filled  it with ferrite which helped greatly. However, I assumed it was the
>slight  bit of AM modulation being detected. The antenna was a six bay end
>fed.
>
>Why is end fed a problem in this way and center fed  not?
>
>
>
>Jeff & others:
>
>The audio and sound guys have fought with the RFI problem for year blaming
>the broadcasters for excessive power etc.
>
>When the real problem has been poorly designed audio gear.
>
>Some years ago we had a LOT of problems with RFI getting into small 16
>channel Mackie Mixers, as well as some of their large sound consoles. 
>Ferrites  and
>all sorts of other tricks were used with some degree of success.
>
>Jim Brown of Audio Systems Group in Chicago _www.audiosystemsgroup.com_
>(http://www.audiosystemsgroup.com)  has a  great web site with 
>downloadable pdf
>files on hum and noise in audio systems.  One issue is the improper design of
>audio gear where the pin 1 inputs of audio  gear are not immediately 
>bonded to
>the chassis of the gear itself! Give the  ground a nice loop inside of the 
>box
>and at RF frequencies, you have a great RF  signal injector at AM or VHF
>frequencies!
>
>I suggest that those who encounter this type of problem with their gear
>check it out more closely.
>
>
>
>Russel L.  O'Toole, P.C.
>R&M Consulting
>
>31 Ponderosa  Drive
>Romeoville, Illinois 60446
>815-372-1990 voice
>630-699-2965  cell
>815-886-9232 fax
>KD5OAE General
>
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