It seems that most PC headsets connect the tip and ring together, so
they can take bias from either, and that connecting the tip and ring
when bias is turned on in the KX3 creates some anomaly. Fortuitously,
the voltage on the ring, presumably pull-up intended for the PTT
input, seems to suffice as bias.
I had a custom Y adapter in my junk box that split a TRS plug to two
TRS sockets, with the tip going to one and the ring to the other (for
cloning an Icom 2m/440 mobile). When I connect my PC headsets through
this adapter (so breaking the ring connection) they work normally with
respect to KX3 bias configuration.
73,
~iain / N6ML
On Mon, May 13, 2013 at 8:14 AM, GDanner <gdan...@windstream.net> wrote:
> Peter,
> Bias is "added" to the tip via menu.
>
> The voltage you read on the 1st ring is the pull-up for the PTT & UP/Down
> buttons.
>
> See the schematic for the MH3 microphone (
> http://www.elecraft.com/manual/MH3%20Rev%20A.pdf ).
> It does show the connections to the mic plug.
> I can not find the Mic jack on the KX3 schematics.
>
> I used the MH3 schematic to make an adapter to interface my K3 microphones
> in case I need my KX3 to back-up my K3 & KPA500.
>
> 73
> George
> AI4VZ
>
>
>
> -----Original Message-----
> From: Peter Eijlander (PA0PJE)
> Hi Dom,
>
> 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.
>
> . . .
>
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