[Milsurplus] Dynamic Mics and powered speakers

[Michael Tauson]

Okay, color me an idiot.  Or some close facsimile thereof.

My total experience with microphones (discounting the ones that were
supposed to be attached to a few CB sets but weren't always) was with
the carbon mics we used in airplanes.  But now I've come up against
the various new rigs that use dynamic mics and I've come up against
something odd.  Apparently there are two flavors, low impedance and
high impedance, with each fairly broadly defined but orders of
magnitude apart.

Sticking with low impedance for the moment, the range I've seen so far
is roughly 150 to 1200 ohms.  Can these be freely interchanged or is
there something else I need to watch as well?  The reason for this is
that I would like to be able to swap mics (with the appropriate
connector adapters) between the PRC-74B, the SEG-15D and the 2M rig
(an older Standard) without problems.  This will make spares a lot
easier (one spare for all three sets instead of one for each set) plus
allow for possible audio switching and one mic if I get carried away
enough.

I've been looking at the AM-4979 and -6747 for use in the Jeep.  It
appears that the 28 volt input is dropped to 12 volts to power the
amplifier which implies that I could just as easily operate it from a
12 volt source.  Is this accurate or am I missing something important?

Best regards,

Michael, WH7HG