[Elecraft] Computer mic for K2 -- no joy

[Don Wilhelm]

Lenny,

What did you use for the bias resistor?  Those computer microphones use 
an electret element which need a bias voltage.  A 4.7k to 10k resistor 
from the AF pin to +5 volts is necessary for the mcrphone to work.

I am not certain why your "2.2k to 1.5V" bias supply did not work, but I 
encourage you to try using the internal +5 volt supply on the K2 front 
panel board to supply the bias (through a 4.7k to 10k resistor).

73,
Do W3FPR

On 1/9/2012 9:56 PM, w2bvh wrote:
> Hi
>
> I got a Logitek headset / boom mic for the K2, figuring it would be less
> fatigue than my D-104 during the upcoming VHF contest. But no joy. E.g.
> no modulation at all even with ssba=3.
>
> Looking at  the output of the mic on scope set to 50 mV per division,
> nothing is visible. I figured maybe its a factory defect so I tried my
> son's Logitek desk mic on the scope and also see nothing. I even tried a
> 2.2K resistor hooked to the tip connection of the desk mic and biased it
> with 1.5V from a bench supply, thinking maybe its an electret. Still
> nothing.
>
> The D-104 with internal amp shows about 150 mV on peaks. And a Radio
> Shack electret element with a2.2K resistor and 1.5V bias gives even more.
>
> So what is it about Logitek mic's (or is it computer headsets in
> general)? Should I return it? The set is light and comfortable and I'd
> like to keep it if it can be made to play.
>
> TIA.
>
> 73,
> Lenny W2BVH
> K2 sn 1520
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