[ARC5] Carbon Mic Replacements

[Mark K3MSB]

Gents

Thank you for all your responses;  you've given me more than a few options!

Chris

I'm intrigued by your comments in particular.  I have the following gear
stashed in the pile:

Shure SM58 Mic
Phonic PEQ3300 Equalizer
CRL  PMC-300A Peak Modulation Controller
Ultra-Voice Pro VX2000 Preamp / Precessor

Old stuff, but it's available!   Getting an audio chain set up and working
would not only help me with the ARC-5, but would also allow me to have
another option for my B&W 5100B (currently using a D-104 with a replaced
mic element).

Getting the ARC-5 on AM is one of my spring / summer project so I'll post
updates to the group.

73 Mark K3MSB


On Fri, Mar 25, 2016 at 3:31 PM, Chris Bowne <aj1g at sbcglobal.net> wrote:

> You might consider feeding it with audio from a external audio chain
> through a suitable isolation transformer and a series decoupling cap to
> block the DC carbon mike excitation from feeding back into the coupling
> transformer winding.  I have been doing this with my command set and TCS
> systems in the shack for years.  I use a small mono utility amp fed by a
> small Rat Shack octave octave band EQ, into a 600 ohm line to voice coil
> transformer hooked up in reverse.  In my setup I feed the external audio
> into an old RM-12 remote control unit that was designed for and used with
> the BC-191 in the field to couple a field telephone circuit into the carbon
> mic input of that set.  I just connect the external audio chain to one of
> the two parallel telephone circuit input terminals on the RM-12. The RM-12
> is a great little accessory to use for this purpose.  It has a level
> setting pot and a VU meter along with a TX/RX toggle switch along with
> jacks in which you can plug in a local T-17 type or any similar military
> carbon miles and a key jack as well.  Can be used with any mil transmitter
> of the era that takes T-17 or similar carbon mic.  I you can't find one you
> can easily do
> the audio transformer and series cap
> arrangement.  You will be a amazed
> how good the audio from the class A 1625 in the BC-456 sounds fed this way!
>
> Sent from my iPhone
>
> On Mar 24, 2016, at 21:14, Mark K3MSB <mark.k3msb at gmail.com> wrote:
>
> Hi All
>
> I want to start using my SCR-274N on AM and have been looking for ways to
> use non Carbon Mic with the BC-456 modulator.
>
> There was a potentially interesting solution about this on an old QRZ.com
> post:
>
>
> http://forums.qrz.com/index.php?threads/carbon-mic-replacement-for-mily-transmitters.443437/
>
> with the schematic (no documentation) listed here:
>
> http://forums.qrz.com/index.php?attachments/img312-jpg.190336/
>
> I went to the ER Web site and there doesn't seem to be relevant article in
> the August 1990 issue.  Does anyone have this issue to verify?
>
> I was also looking at back issues of ER and the only two related articles
> I found were:
>
> January/1992  Microphone Replacement, TCS Carbon by (Mike?) Murphy.
>
> March/2008  Regular Mic preamp for Carbon-Mic-Only Transmittters by
> Heidelman.
>
> I don't have any of these back issue in my collection, and I'd be
> interested in know if any of those articles provide a suitable solution to
> using a non carbon mic.
>
> 73 Mark K3MSB
>
>
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