[Milsurplus] SIMPLE Carbon Microphone Substitute.

[Mike Feher]

Dave -

I am actually surprised that circuit works with nothing but the base of the
BJT going to one side of the electret I would at least expected to see a
resistor, audio bypassed, in the emitter, and, a high value resistor from
the base to ground. But, it is hard to argue with "it works" HI. 73 - Mike 

Mike B. Feher, N4FS
89 Arnold Blvd.
Howell, NJ, 07731
732-886-5960 

-----Original Message-----
From: Milsurplus [mailto:milsurplus-bounces at mailman.qth.net] On Behalf Of
David Stinson
Sent: Saturday, May 28, 2016 10:25 AM
To: milsurplus at mailman.qth.net; boatanchors at mailman.qth.net
Subject: [Milsurplus] SIMPLE Carbon Microphone Substitute.

Been working on a simple substitute for the Carbon microphone used with the
BC-669.  I've seen some multi-IC, 3-dozen-part designs which hugely violate
The Law of Pernicious Parts Count:
     "Every part in a project beyond about eight
     reduces the number of people who will build it
     by 50%."
So no one builds them.  I hope this one will get tried and improved:

https://goo.gl/photos/26HUmzVuqhZKWrNZ7

Cobbled it together and it works well with the BC-669.
I picked that transistor because it was the first one I grabbed from the
"NPN Small Signal" drawer and my Android phone called it "General Purpose."
Other common NPNs will likely work as well.
The electret element isn't mark +/-.  I soldered it in one way and it didn't
work.  Turned it around and it did.
Will try it on other rigs as the weekend goes on.

73 DE Dave AB5S
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