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

[Don Wilhelm]

Ed,

For use with the KX3, I would believe the audio generated PTT signal 
such as shown in Skip Teller's interface at 
https://sites.google.com/site/kh6tyinterface/ would be the preferred PTT 
solution.

My reason is that the KX3 USB data cable includes only TXD and RXD. If 
you use RTS or DTR for PTT, you are forcing the user to have a full 
serial port (and not the KX3 USB cable).

Yes, you can use a Y adapter to feed a real serial port or a USB to 
serial adapter to both the KX3 serial cable and to the data interface, 
but that gets complicated.

I would suggest you use some variation of Skip Teller's interface which 
generates PTT from the audio stream, or since the KX3 VOX is good, 
simply use the KX3 VOX and just put transformers in the audio lines.

Edm I an certain others would be interested in your implementation, so 
if you would be so inclined, get up a list of parts for your design and 
see if someone like FAR circuits would be interested in building some 
sheets of boards for you.  Presto, good data mode interfaces for the KX3.

73,
Don W3FPR


On 7/12/2012 8:50 PM, Edward R. Cole wrote:
> 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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