[Elecraft] Replacement Hand Microphone

[Augie Hansen]

On 7/20/05 3:44 PM, "Stuart Rohre" <rohre at arlut.utexas.edu> wrote:

> You can either use a high impedance to low transformer for the D104 mike, or
> get one of the D104 "amplified" mikes which has a impedance converting
> transistor circuit in its base, able to drive low impedance modern
> microphone inputs.
> 
> The crystal high impedance element of the 104 needs to look into a high
> impedance to avoid altering the tone response.  It will sound good, if
> properly terminated into the right circuit.

Alan, W2AEW, has a very nice construction article on one of his web pages:

    http://www.qsl.net/w2aew/myd104amp.html

We've talked on air several times and his audio is excellent.

If you have a D-104 with a functioning crystal (or ceramic) element, this
circuit is a good way to match the hi-Z output to the low-Z input of modern
rigs. Alan has been careful about RFI proofing and other essentials, such as
tone characteristics and gain control.

At the end of the page is the schematic for the original Astatic preamp.

73, Gus Hansen / KB0YH