[RFI] Subwoofer resolution

Jim Brown jim at audiosystemsgroup.com
Sun Aug 19 12:54:26 EDT 2007

On Sun, 19 Aug 2007 11:40:37 -0500 (CDT), Craig Thompson wrote:

>I tested the Sub Woofer/ "science experiment" by lowering my 2m EME array
>to 24 feet (21 DB gain) and aiming it right at the box in my driveway and
>putting 15002 to the antenna running FSK441, not a peep!! 

A 2M/440 talkie, Nextel phone, and Blackberry used as a signal injection 
probe around the device and its I/O wiring are very effective. It might be 
worth owning a 6M talkie so that one could use it that way. There's an AES 
paper on my website that documents my testing of about 40 rather expensive 
professional condenser mics in this manner. I moved the talkie and cell phone 
antennas along the mic cables to find the peaks in the voltage and current 
distribution that would excite the susceptibility in the mics. I've done 
similar testing of amplified loudspeakers and other professional and consumer 
electronic products. 

BTW -- this paper turned the microphone industry upside down with respect to 
RFI. It turns out that the dominant cause of the susceptibility was a pin 1 


Jim Brown K9YC

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