I might add that if one has an amplified D-104, but wants to remove the
dependency on the battery in the base, that single FET addition can
replace the amplifier in the mic. Yes, I have done that in one of my
D-104 mics. It also works for the K2 when the microphone configuration
header is wired for the Elecraft MH2 microphone (with the bias resistor).
73,
Don W3FPR
On 1/28/2014 8:58 AM, Joe Subich, W4TV wrote:
The easiest way to use an unamplified D-104 with the K3, or replace a
bad/noisy transistor preamp is this single FET circuit from W9AC:
http://72.52.250.47/images/D104.pdf
The single FET is uniquely suited for the high impedance crystal
element and "bias on the mic" power. When handled properly the
Astatic crystal element is far superior to the commodity dynamic
elements sold at tremendous mark-up by the "name" amateur vendor.
73,
... Joe, W4TV
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