29/05/2016

Very Simple Straight Key

I used to have a very simple "emergency" key with my KX3, just a pushbutton (the TURBO switch from an old PC, remember the days when PC's had a turbo mode ?).
I didn't use it very much because it has a bit too much travel for good keying ...

I did make several paddles in the past, all made from scrap pieces of PCB.
One of those was made after the idea of Carel PA0CMU for a double paddle : http://members.ziggo.nl/cmulder/paddle.htm
Carel based his design on the idea of  NB6M for a single paddle :
http://www.amqrp.org/projects/paddle/NB6M%20Paddles.html

So I got the idea to make the simplest straight key, and still have good results. This is what I came up with ... you need :
- 2 pieces of single sided PCB, approx. 2 x 5 cm, may vary along your taste ...
- Two contacts from an old relay (cleaned with a blue ink eraser)
- Dremel cutting tool
- Soldering iron
That's it !

I took a picture when everything was cut to size, ready to start soldering.
(I didn't make a drawing, just drew some lines without even measuring , hi)



I took the two small pieces for the side posts from another piece of PCB,  but you could actually cut the center piece in two. The excess PCB of these post will be cut off later anyway.

First solder the contact strips in place (take care : don't put solder on the contact points !).
Then mark two lines on the bottom piece and solder the posts in place.
(this picture is from a second model with wider "arms" for some more resistance)
Also remove a strip of copper to isolate the front contact from the rest (all the rest will be GROUND).
















Then put some spacer between the contacts and hold both parts in place with a clothespin, like this:



If you are satisfied, solder the arms in place, they can easily be repositioned later if the contact distance is not what you like.

Then put a capacitor of 10nF over the "gap" and connect a cable with a 3.5 mm jack.
For my KX3 I have to use a STEREO jack, but using only the tip and sleeve connections, this may differ for other brand of transceiver.

I made two different keys, one has a fixed cable, the other has a 3.5mmm connector, to be used with a seperate cable. I can fit both this key AND a mini single-lever paddle in a film can !
















Have fun !

Luc ON7DQ/KF0CR

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