[NLRS] Mic

[Dr. Gerald N. Johnson]

Insufficient information. It could be dynamic, or electret. The 
diaphragm for a dynamic element usually tends to show a ring of smaller 
diameter than the edge of the diaphragm where the voice coil is 
attached. And an electret tends to not show that ring on the surface of 
the diaphragm. The DC resistance of the electret may be polarity 
sensitive. The dynamic element in the old days tended to have a very low 
impedance, like a few ohms, and then have a transformer in the 
microphone to step up impedance and voltage probably to a few hundred 
ohms. The radio input for the dynamic won't have any open circuit 
voltage. The radio input for the electret will have a few volts behind 
typically 680 ohms. You really need to radio or the radio model number 
to be able to make a fix.

On 8/20/2013 9:35 AM, S. Earl Jarosh wrote:
>
>
> I am trying to fix a Mic for a friend of mine who has a marine radio on his
> boat.  He gave me the Mic and the Label on it is "ifr" that is all I got.
> The element reads open and that follows through with the fact that he can
> key up the radio but no audio goes out.  I am trying to determine what kind
> of mic element it is so I can put one in with the correct impedance.  It is
> a metal housing with a metal diaphragm.
>
> Any ideas??
>
>
> S. Earl Jarosh, N0HZ
> SEJ Industries, Computer Consulting
> 1432 Quebec Ave N
> Golden Valley, MN  55427
> Cell:  612.868.1313
> Off:   763.545.3275
> Fax:   763.546.7897
> 6128681313 at txt.att.net
> earl at jarosh.org
>
>
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