HDP-121A Microphone Impedance???

[John H. Klingelhoeffer]

Fellow Heathens:

I have a Heath HDP-121A microphone that I would like to use with a
from-scratch transceiver that I am building.  This is the "old"
desk-standing, grey cased microphone (I think sourced by Shure) that was sold
as the desk mike for the SB and HW series transceivers.

I'd like to present the optimum input impedance to the microphone to give it
the best response.  I have the original instruction / specification sheet for
the microphone, and it only states that the microphone impedance is, quote,
"Hi-Z".  Not quite specific is it ? !   I am presuming if this were a "low Z"
microphone, such as that used on solid state transceivers that "low" would be
200 to 600 ohms.

I'm guessing from taking a look at the input circuit on my HW-18 (which used
the same series of microphones as the SB and HW series) that what the
microphone would "like" to see is maybe something around 100k ohms or more.
Some phono inputs are set at 47K ohms, and that would also be "high" in my
thinking, relative to 600 ohms.

Anyone know what "Hi-Z" translates to for this microphone?   Thanks in
advance for your responses.

John...
WB4LNM
One of the Hams from Heath (1979-1981)
Gambrills, Maryland

Sponsored by the City of Tempe 

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