[Milsurplus] Dynamic Mics and powered speakers

[Brooke Clarke]

Hi Michael:

In general if the military connector fits U-77 or U-229 then the audio 
equipment is compatible.  The U-77 is a carbon mike system that pretty much 
follows telephone practice.  The U-229 is a dynamic mike system.
http://www.prc68.com/I/Audio.shtml#U77
http://www.prc68.com/I/U229AA.shtml
http://www.prc68.com/I/U229PO.shtml

The AM-6747 was made to use with the KY-65 and is an amplified LS-454 with an 
added relay to stop the speaker from sounding the clear text.
You can power it from 12 or 24 volts depending on how you wire the power connector.
http://www.prc68.com/I/KY65.shtml#AM6747
http://www.prc68.com/I/LS454.shtml
http://www.prc68.com/I/AM4979.shtml

Have Fun,

Brooke Clarke, N6GCE
http://www.PRC68.com
http://www.precisionclock.com
http://www.prc68.com/I/WebCam2.shtml 24/7 Sky-Weather-Astronomy Cam


> Date: Wed, 14 Nov 2007 11:41:18 -1000
> From: "Michael Tauson" <wh7hg.hi at gmail.com>
> Subject: [Milsurplus] Dynamic Mics and powered speakers
> To: milsurplus <milsurplus at mailman.qth.net>
> Message-ID:
> 	<c34299fb0711141341g196d3580ue769195d08fa9a47 at mail.gmail.com>
> Content-Type: text/plain; charset=UTF-8
> 
> 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