[Elecraft] Digital Mode Interface for the KX3 for WSJT modes

[Edward R. Cole]

Don,

After making several sound-card interfaces (never have used a 
commercially made one),  I deduced the "surest way" to avoid audio 
problems was by total isolation of computer ground and radio 
ground.  East to accomplish using isolation transformers for audio 
and opto-isolators for dc controls.

I guess there are applications for a "VOX-like" PTT control, but I 
use RTL or DTR lines for this with the sw I run.  Opto-isolator like 
the 4N36 work well in this path.

I am going to go ahead making up an I/F with tiny pcb transformers, 
but probably not try installing all inside a sub-D 
connector  (commonly called DB-9 or DB-25).  I will use a tiny 
plastic box and small pc board with mini-phone connectors for audio 
and DB-9 for RS-232 interface.  I have in mind that it will attach on 
the back of the KX3 with a velcro-patch (so one can remove it at will).

I am just stacked up at present so this will not be worked on 
right-away (assuming Lance has one for his eme dxpedition).

I am writing a power-point presentation to demo the KX3 this 
weekend.  I'll add it to my website afterward.

73, Ed - KL7UW

At 02:49 PM 7/12/2012, Don Wilhelm wrote:
>Thanks, yes that is the one that produces the PTT from the audio stream.
>I note that Skip no longer has kits and boards, but he has supplied 
>a complete parts list and the circuit is simple enough to wire on 
>perfboard.  The photos provide a nice layout guide.
>
>Contrary to K9YC's statements, I believe the transformers are 
>necessary for use with a laptop.
>Jim's "bond everything together" is a great solution (and it works) 
>for the home station using a desktop computer, but bonding the 
>computer becomes more difficult when using laptops with all plastic 
>cases.  I cannot find a good place to connect to the computer ground 
>of my IBM Thinkpad.unless it just happens to be the jackscrews on 
>the VGA connector - but those are there to prevent connector 
>pullout, and may or may not be grounded.  (I use a desktop at the 
>home station).
>
>73,
>Don W3FPR


73, Ed - KL7UW, WD2XSH/45
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