[Elecraft] KX3 PC Headset Stereo mike

[Peter Eijlander (PA0PJE)]

Hi Dom,

When I plug in the mic of my PC-headset I can operate the vox without 
any problem. MIC BTN=off and MIC BIAS=off...

When I measure the mic connection with a standard 3.5 mm. stereo cable 
with two RCA plugs at the other end, I end up having no voltage on the 
tip of the 3.5 mm plug and 2.4 volts on the middle ring. That is the 
situation I'd expect it to be: These mics are usually wired for mic 
inputs of soundcards and they carry the bias supply voltage on the 
middle ring and the AF output comes from the tip.

Switching on the MIC BIAS ads an audible noise on my monitor as does 
setting the MIC BTN either to PTT or to PTT UP.DN.

Of course in the MIC BTN=off you have no PTT function on the plug 
available, so use of VOX is the only option to transmit.

In fact the PTT function is off but the logic level stays high and that 
supplies the microphone with the necessary bias form the VPTTUPDN line 
that comes straight from the PIC U10 via a 1k resistor if I understand 
the schematic part 'KX3 Control Panel: Connectors' right.

I don't know whether J8 in the drawing signifies the MIC connector but I 
doubt that for it does not have that extra ring on on the MH3 microphone 
plug for nothing. I looked through all drawings but could not find that 
connector.

Maybe someone else can fill in the gaps...?

72/73,
Peter - PA0PJE

dombaines at yahoo.com schreef:
> HI,
>
> KX3, I have played about with the two mike settings BIAS (on/off) and
> pgupdwn/ptt/off with a computer headset where the 3.5mm mike has a
> stereo plug and no joy. Noted it initially as got the PTT error message
> and TX stays open when plugged in. No amount of combinations of with VOX
> on/off and setting the mike options seems to make it work where pressing
> the PTT on the KX3 keys the mike (or VOX does).
>
> A stereo to mono adapter doesn't seem to help.
>
> Anyone had a similar problem and got a cure?
>
> The headset is identical to another I have as I wanted to get a second
> set (for second KX3) but the earlier one has a mono mike.
>
> I looked at chopping the cable and rewiring (The mike has a tiny + screw
> in it so I undid it just to see how it was wired) but I noted the wires
> are not the easy to solder type.
>
> 72
> Dom
> M1KTA
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