[ARC5] Carbon cartridge replacement circuit

[Richard Knoppow]

    An ohm meter reading won't tell you much. Both a dynamic or carbon 
mic will have resistance of similar value.  Carbon microphones were used 
for many decades because they are fairly simple to make but mainly 
because a carbon microphone is also an amplifier so the mic has very 
high output and does not need as much amplification as other types do. 
This was important when electronic amplification was expensive.
    Carbon microphones were replaced with magnetic or dynamic types. 
Magnetic microphones are simple and very rugged. Of course, in recent 
years, most types have been replaced with electret mics with a small 
solid state amplifier or impedance matching circuit. These are 
especially suitable for replacing carbon microphones because they can be 
powered from the carbon mic bias supply and can have equally high 
output. They are very simple, cheap to make, have good fidelity and are 
very rugged.

On 4/27/2017 10:51 AM, Roy Morgan wrote:
> J,
>
> I have more than one microphone used in Navy planes (helicopters) in the
> 60's and 70's.  I am not sure if these are carbon microphones or dynamic
> ones (we did use little inline amlifiers at about that time with some of
> the lip mikes we had.)
>
> Can you give any hints as to how to determine which is which?
> Resistance maybe? One is gray and another one or two are black.  They
> mounted on the helmets.
>
> Oh yes, I will look on them for some sort of nomenclature - I bet I'll
> find something.
>
> Roy
>
>
> On Mon, Apr 24, 2017 at 9:06 PM, J Mcvey via ARC5 <arc5 at mailman.qth.net
> <mailto:arc5 at mailman.qth.net>> wrote:
>
>     Hello all ,
>
>     I finally got this drawn up and published.
>     This circuit will produce up up to  about 4 vpp without clipping.
>     It has  more than enough gain to produce maximum modulation without
>     yelling into the mike.
>     Enjoy;
>
>
>
>
>     https://www.mcveyelectronics.com/images/stories/pdf_files/electret_carbon_rpl.pdf
>     <https://www.mcveyelectronics.com/images/stories/pdf_files/electret_carbon_rpl.pdf>
>
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> --
> Regards,
> Roy
>
> Roy Morgan
> k1lky since 1958
>
>
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-- 
Richard Knoppow
1oldlens1 at ix.netcom.com
WB6KBL