[Elecraft] [KX3] MIC Bias has no effect

[dmb at lightstream.net]

Thanks to all for the responses. It makes sense, and yes, I do find that
the mic is 'hotter' w/ the Mic Bias turned off.  I had already been using
the noise gate so that's probably why I didn't notice the little bit of
extra noise. All sounds good.

73, Dale
WA8SRA


> I saved this detailed note that was posted on this list a couple of years
> ago. Maybe Elecraft needs a KX3 FAQ with this info.
>
> ------------
> Re: KX3 - Buzzing in headphones varies with MON level
> Posted By: kk7p
> Date: Wed Jun 20, 2012 12:49 pm
>
> I dragged out my CM-500 to test this.
>
> The CM-500 gets its mic bias from BOTH the tip and the ring of the gray
> mic
> connector. This is too bad, because the tip voltage is controlled by the
> MENU:MIC BIAS ON|OFF but the ring is always biased by the PTT/UP/DN logic
> supply.
>
> To get around the problem, do the following:
>
> 1) MENU" MIC BIAS OFF
>
> You will find you need a lot less Mic Gain for full ALC action. In my KX3,
> I
> need about 30 if BIAS is ON, and 17 if BIAS is OFF, for full ALC.
>
> 2) Since the PTT/UP/DN is a digital logic supply, it may have some
> residual
> noise that the CM-500 passes as audio to the tip of the connector.
>
> Go to MENU: TX GATE and tap "1" to turn it ON then adjust VFO A for 01 or
> 02,
> whatever it takes to kill the residual buzz.
>
> In the case of my KX3 + CM-500, this cured the problem. And in Dave's
> case, it
> might not cure the problem of noisy neighbors, but will allow the KX3 to
> better
> ignore them!
>
> 73,
>
> Lyle KK7P
> ----------
>
> Thanks, Lyle.
>
> wunder
> K6WRU
>
> On Apr 19, 2014, at 9:27 AM, "dmb at lightstream.net" <dmb at lightstream.net>
> wrote:
>
>> I'm connecting a Yamaha CM500 headset to the KX3, and find that the
>> microphone works properly regardless of the MIC BIAS setting (MIC BTN is
>> set to OFF).
>>
>> As I recall, the few times I used the CM500 w/ the K3, the MIC BIAS had
>> to
>> be ON or the microphone produced no output.
>>
>> Any idea why the MIC BIAS setting doesn't seem to matter w/ the KX3?
>>
>> 73, Dale
>> WA8SRA
>>
>>
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>
> --
> Walter Underwood
> wunder at wunderwood.org
>
>
>
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