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

[Lance Collister, W7GJ]

Thanks for all the comments and suggestions.  I will continue to explore the 
possibility of an ultra-compact solution by just breaking out cables from a DB9 
connector.  However, in the interest of time, my first interface will use the 
RIGblaster Plug & Play unit from West Mountain Radio.

This compact unit provides a USB interface to the computer, plus completely isolated 
audio lines for input and output and  isolated RTS (for PTT) and DTR (for true CW) 
keying from the computer. This interface also already includes a stereo jack for CI-V 
rig control, that appears to be directly compatible with the ACC1 jack on the KX3, so 
that is one less breakout connection I need to build!  It also already has a separate 
jack for a speaker, so I can listen with headphones at the same time as the 
computer.  This is especially handy when copying CW and still needing the audio to be 
fed to the computer so it can display the spectrum with a waterfall program such as 
Spectran.

I have already ordered a couple inexpensive female DIN connectors from Digikey to 
connect with the output "ACC PLUG" line from the RIGblaster Plug & Play unit, and 
from there I will simply run a line to the KX3 Headphone Jack (for the audio out) and 
another shielded stereo cable to the KX3 4 pin microphone plug (for audio and PTT 
into the KX3).   I will use the KX3 ACC2 jack to key my amplifier.

I know there are others on this list who are interested in operating digital modes 
with an RTS line advance PTT keying capability, and I will provide photos and results 
as soon as I have everything completely assembled and tested.

VY 73, Lance


On 7/11/2012 4:48 PM, Lance Collister, W7GJ wrote:
> I am still waiting for my KX3, but I imagine with over 600 of them out in the 
> field, SOMEBODY must have experimented with an interface for running WSJT modes.  I 
> will need to build up the custom interface cables as soon as my KX3 eventually 
> arrives, and I won't have much time left to troubleshoot or re-do things.  So I 
> sure would appreciate any suggestions or guidance anyone with experience on their 
> KX3 may be able to provide.  I am HOPING there might be some way to simply use 
> resistors to pad down the computer LINE OUT and isolate it enough to work with the 
> KX3 MIC INPUT.
>
> I realize I will have to break out several of the serial port lines from the 
> computer DB9 and connect them to various jacks on the KX3.  The TX (pin 3) and RX 
> (pin 2) obviously must be connected to the ACC1 plug ring and tip, respectively.  
> Do I just connect the sleeve of the ACC1 to both the SIGNAL GND (pin 5) AND the 
> SHELL ground/cable shield?
>
> For the ACC2 plug, I am planning to use the RING to turn on my amplifier, and the 
> TIP will be connected to RTS (pin 7) of the computer serial port.  Wayne had 
> mentioned before that there should be a 2200 ohm resistor between the tip and the 
> RTS line connection.  I assume the sleeve of the ACC2 is connected to both SIGNAL 
> GND (pin 5) AND the SHELL ground/cable shield?
>
> Of course, the KX3 HEADPHONE line will go directly into the computer LINE IN - no 
> problem ;-)
>
> I am planning to connect the computer LINE OUT to the tip and sleeve of the KX3 MIC 
> jack.  However, in K9YC's interface manual, he suggests, putting a 4700 ohm 
> resistor in series with the tip, and putting a 470 ohm resistor from tip to 
> sleeve.  Has anyone tried this yet on digital modes with the KX3?  Does this 
> provide enough isolation and prevent hum?
>
> I see in the manual that a power cable with a 2.1-mm plug is supplied, so I can use 
> that when I receive my KX3.
>
> I would greatly appreciate input from anyone who has already "broken trail" on 
> building these KX3 interfaces ;-)  MNI TNX and VY 73, Lance
>


-- 
Lance Collister, W7GJ
(ex WA3GPL, WA1JXN, WA1JXN/C6A, ZF2OC/ZF8, E51SIX, 3D2LR, 5W0GJ)
P.O. Box 73
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USA
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