Using SONY ECM-21 Mic on AM or SSB?

[Stewart Lyon]

On Sat, 18 Dec 1999 20:07:37 -0500 DavidC <eDoc at NETZERO.NET> writes:
>I have come by a pair of SONY ECM-21 microphones.
>They are cardioid pattern electret condenser microphones.
>
>Can these be used for AM or SSB modes?  Do they need to
>be run through a pre-amp and some sort of processing?
>
>Rigs I would want to try these with are:  Elmac AF-67, Morrow MB-560,
>Tempo One/FT-200, Kenwood TS-690S/AT.

>- Thanks! & 73, DavidC  K1YP

Most electret mics require 4-5 volts DC with a load of 2.2K to 5K. I
installed a RadioShack electret element in a D104 that had a bad crystal
and I powered the mic from the 9 volt battery that was in the mic stand.
For the load I used two 4.7K resistors in series across the battery with
the mic connected at the resistor's center tap. Since there is a DC
voltage (~4.5v) at the mic output, a capacitor is required in series with
the output. The electret seem to have about the same output level as
another D104 with a new crystal element so you may not need an amplifier.
But you will need a dc source (which some rigs supply at the mic jack)
and a load resistor.

73, Stu W6CUX