Saturday, March 16, 2019

Adapting the Elecraft KX3 and KX2 for two keys - two keys / paddles or paddle plus computer keying

The Elecraft KX3 and KX2 have two CW paddle inputs, individually configurable. This is great, especially for contest operations which typically require one input for the computer and one for a paddle. In this article, I'll describe how adapt the KX-3 for two separate CW inputs. 

I recently operated in the 2019 ARRL DX CW contest from Belize with my KX-3 driving an SPE 1.3k amp. This was the first time I've used the KX-3 in a contest or DX trip and I was impressed with its performance and features. Before this trip I didn't even realize the radio has dual watch, something the K3 doesn't provide as a standard feature. I used it when I was running pileups and it worked very well. This radio is really more than meets the eye.

Another great feature of the KX3 is two individually configurable paddle inputs. There's just one problem, the front panel header, Key2, mates with a non-standard connector for Elecraft's accessory paddle. To solve this I purchased the matching 4 pin header off of Ebay. The finished adapter, shown below, consists of a molded 3.5mm stereo jack wired to the header according to the wiring instructions provided below. To protect the header connections I put heat shrink tubing over the header pins. I used a hot glue gun and filled the tubing with a bit of glue and slid it over the pins. The hot glue shrunk the tubing somewhat and then I used a heat gun to fully shrink it. The finished adapter is shown below. The two key inputs can be configured for hand-key, or paddle. I configured Key1 for the computer (hand key) and Key2 for the paddle. The dot and dit pins are menu configurable, don't worry about getting them reversed. The wiring instructions (when viewing the radio pins) are as follows: Upper right=ground; Upper left=none; Lower right=dah; Lower left= dit.




The finished adapter cable

This is the description of the connector taken from the ebay listing:

2.54mm Pitch 2X2 4 Pin Female Double Row Straight Header PCB Connector 284

PS - I had to purchase 50 of these. So, as of this posting, I have plenty of surplus.  If you are reading this, I still have some. If you want one FREE, just send me an SASE.