[Elecraft] Astatic D-104 Microphone

[Don Wilhelm]

D-104 microphones with the amplifier in the base work just fine with 
modern rigs.  Look at the bottom of the microphone - if it has a hole 
with an adjustable potentiometer below the hole, it has the amplifier.

The Heil rebuild kit is not needed unless the mic element is bad. The 
frequency shaping of the Astatic mic element is very similar to the Heil 
HC-5 mic element, but the Astatic element needs to work into a high 
impedance (100k to 1 megohm) to preserve that shaping. In an all-tube 
transmitter, that high impedance was presented by the grid of the 
microphone amplifier.
Those D-104 mics with an amplifier will work into a much lower impedance 
mic input without any change.

The old crystal elements could go bad if exposed to temperature extremes 
or rough handling, but the more common ceramic elements are practically 
indestructible.  Astatic made these microphones over a long period of 
time dating back to the 1950s or before, and there were changes from 
time to time.

73,
Don W3FPR

On 1/28/2014 8:40 AM, John Fritze wrote:
> I am currently in the middle of converting a D-104 Eagle into a usable mic
> and have had a bit of experience in the past with them.  I am trying to
> recapture a bit of the nostalgia from my early ham days.  I paid too much
> for it, but not only is the chrome flawless, but it came with the original
> box which surprisingly is in really good condition.
>
> Anyway what Don says is true, there were several models and until you
> dismantle it you will not know what one you have.  BUT on the plus side,
> when I removed the bottom plate, "looky-looky" there was a schematic
> diagram pasted to the inside with the wire colors for my model listed.  My
> mic had a large element (probably carbon) and an amplifier circuit with 9V
> battery (still in there---yuck) in the base.  So remove the bottom, and if
> there is no schematic, but your mic sounds like it is the same model I
> described, let me know and I will try to send you a picture of the
> schematic.
>
> I ordered a Heil 5.1 rebuild kit from: * http://www.dxstore.com/heil_parts.html
> <http://www.dxstore.com/heil_parts.html> * for $50.  I needed some small
> parts for several of my older head sets like foam pads and so forth, so
> perfect timing.
>
>
>