[Milsurplus] [ARC5] mike current

[Ray Fantini]

They may have been around for over a hundred years but carbon element microphones have not been used in broadcasting for well over fifty years, cannot recall them being used in commercial radio for at least as long and thought the telephone system stopped using them by the seventies or eighties, just try to find a desk set land line phone today! Especially one with real carbon elements.

Also amazed to see the TCS people have their own list, thought the ARC-5 group were specialized.

Ray F

-----Original Message-----
From: milsurplus-bounces at mailman.qth.net [mailto:milsurplus-bounces at mailman.qth.net] On Behalf Of mac
Sent: Wednesday, September 07, 2011 3:55 PM
To: ARC-5 List; Boat Anchors List; milsurplus at mailman.qth.net List; TCS_Radios at yahoogroups.com
Subject: Re: [Milsurplus] [ARC5] mike current


These things have been around for over 100 years now and there gotta  
be a large body of science and art out there in the technium on the  
composition, manufacture, etc. of just the carbon granules not to  
mention the microphone elements themselves.  I've observed a wide  
variation in the external characteristics (at least) of the elements  
found just in the venerable T-17 not to mention the many thousands of  
telephone, broadcast and other microphone elements that proceeded (and  
followed) it.   Browsed around on Google a bit and didn't find too  
much except for a reference to a 1934 paper that seemed to say that  
the interaction between granules in response to sound pressure is a  
simple make-break action, i.e., the element resistance overall  
decreases with increasing pressure because more granules come into  
contact with each other, not because increased pressure between  
individual granules lowers the resistance of the individual contacts.   
Anyone have a good reference(s) in this area?

Dennis D.  W7QHO
Glendale, CA
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