[BC] RF interference problem

[RLO2L@aol.com]

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
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