[Elecraft] [K3] Fw: Non Amplified D104

[Ron D'Eau Claire]

Did you use the K3's MENU:MIC SEL option to choose high gain for the
microphone input?

It sounds like the element is good, but they were designed for very high
impedance inputs. A very simple one-transistor amplifier would fix that and
provide a better impedance match for modern rigs. Indeed, impedance matching
was one of the major functions of the amplifier built into the base of the
later D104's. Crystal elements like the D104's were appreciated for their
relatively high audio output which made up for their being very fragile -
easily damaged by a hard knock, high temperatures and moisture. 

If it's an old D104 whose element has survived all these years, it's likely
a ceramic element. Ceramic elements replaced the crystal elements in most
microphones starting shortly after WWII. They are relatively rugged but
provide somewhat lower output. It sounds like your ADI rig had more mic gain
available than the K3. 

Has the mic cord been replaced? I tried that for a buddy who had a D104 with
a badly worn cord. Didn't work at all using modern "shielded microphone
cable". The problem was traced to what's considered a "shield" these days -
a few strands of bare wire wrapped around the "center conductor"! They can
get away with that today for most applications because of the lower
impedance of modern dynamic microphone inputs, but it's hardly a "shield".
Using it with the high-impedance D104 element it picked up hum and lots of
other noises like the "fan noise" you mention. I fixed my buddy's problem by
throwing away the "mic cord" and using RG-174 coax - the miniature stuff -
that has a decent braid shield around the hot conductor.  

FWIW, the D104 has a "starring" role in the new film about Amelia Earhart,
"Amelia". It makes lots of appearances in the hands of people at ground
facilities talking to her in the air. 

Ron AC7AC


-----Original Message-----

I tried a non amplified D104 and it  was not good at all. The audio was real
low when the mike was at 60. It had a slight "fan noise" and I had no fans
running. The mic was wired up right because when I put it back on my ADI
radio it worked well. My ADI radio hand mic works on my K3. ADI and Kennwood
wiring is the same. Now the non amplified D104  is a museum piece in the
shack.