[Elecraft] KX3 cables for microHAM

[Joe Subich, W4TV]

The first version of DB37-EL-KX3.pdf has RS232 in/out and audio
hot/returns reversed.  An updated drawing (identified as revision 2.0)
has been uploaded to the same locations as the original.

73,

    ... Joe, W4TV



On 7/18/2012 10:19 AM, Joe Subich, W4TV wrote:
>
> I have placed drawings for DB15-EL-KX3 (USB II, USB III, Digikeyer,
> and Digikeyer II) and DB37-EL-KX3 (microKEYER, microKEYER II, MK2R+)
> cables in the files area of the microHAM list on Yahoo -
> http://groups.yahoo.com/group/microHAM - and at:
>     http://www.microham-usa.com/Downloads/DB37-EL-KX3.pdf
>     http://www.microham-usa.com/Downloads/DB15-EL-KX3.pdf
>
> Due performance issues in paralleling headphones or (powered) speakers
> with the input of the microHAM sound cards and potential hearing damage
> from excess headphone levels, the microHAM factory have declined to
> produce these cables.  Individual users may, of course, build from
> these designs for their own use but the designs may not be duplicated
> commercially without permission.
>
> The KX3 headphone output is limited to substantially less than 100 mW
> if the audio to remain undistorted (absolutely essential for digital
> decoding).  While the "sound card" in the microHAM interfaces has a
> relatively high input impedance and a low noise, high gain preamplifier
> with transformer isolation that would have no problems working from the
> headphone output by itself, paralleling headphones or powered speakers
> with unknown impedance can certainly cause issues of loading as well as
> hum and/or RF pick-up.
>
> Best results will be achieved by using powered speakers and connecting
> headphones to the speakers (many have headphone jacks).  This way the
> KX3 may be set for undistorted output and listening levels can be set
> with the volume control on the speaker amplifier.  If speakers are not
> appropriate due to weight/space considerations, use headphones with an
> impedance of at least 32 Ohms (the Yamaha CM-500 is 120 Ohms) to avoid
> loading or loss in the KX3's output.
>
> 73,
>
>     ... Joe Subich, W4TV
>         microHAM America
>         http://www.microHAM-USA.com
>         http://groups.yahoo.com/group/microHAM
>
>         support e-mail:  support at microHAM.com
>