A home-made single-lever key

DIY Saw Blade CW Key in a Junction Box

Courtesy of Chris, K2CWC

(This is an abridged version of the complete build article which can be found at the link above. Many thanks to Chris for allowing us to reproduce his work here.)

When I passed my technician license exam I was confronted with the fact that I didn’t have a radio.

Well, I submitted my order with a QRZ-1 Explorer through the GigaParts New HAM promotion. That’s a fantastic deal and I have been thrilled with that radio for portable VHF/UHF use.

Meanwhile, continuous wave (CW) called to me. I was just intrigued with the idea of communicating using Morse Code. The learning and studying leading up to the Technician Exam really sparked an interest and a desire to keep learning.

The Build

Remember, a CW key is just a switch. It closes a contact between a supply voltage and common which, in turn leads to a “continuous wave” (CW) signal being generated by a keyer or keying circuit on the upper side band (USB) of your selected frequency.

My approach to building this “switch” was to aim for a side-swipe or side-shift dual key. Pushed to the left, it closes the contacts for my keyer to produce a DAH. Pushed to the right it closes the contact for my keyer to produce a DIT. Or vice verse, my keyer can accomodate either directional bias.

I started with two hacksaw blades. I used an angle grinder to grind down the teeth on the blade and then used a cutting wheel on the same grinder to cut the blades into 4″ lengths that I thought would work well with my enclosure length of 4-1/4″.

The blade on the left has had the teeth ground down.
I drilled holes on either side of the LB junction box at 1″ and 2-3/4″ from the inlet, right at the parting line of the mold. The holes closest to the outlet (right in this picture) will accept a through-bolt to hold the back end of the blade and provide the common electrical contact. The holes closest to the inlet (left in this picture) will accept individual bolts to serve as the selectable contacts for DAHs and DITs (side-swipe key). By the way, this could (and does) work as a straight key. It all depends on the setup of your keyer which turns the contact closer of this key into a signal.
Here are the two first keys I made in a view that lets you see the basic mechanical layout. One was for me one was for KE2DFG (my brother, Kurt). I’m not quite sure why I ended up with the two front holes not being aligned. I drilled from either side and could have gone straight through to avoid that. I don’t think it matters much since both are independently adjusted for “throw.”

The electrical wiring is best approached remembering that this key is just a double pole, single-throw (SPDT) switch with a center rest. Pushed one way, it closes one circuit (DAH), pushed the other way it closes another circuit (DIT). Without any force on it, it rests in the center with both circuits open (no signal produced).

Here is the basic wiring from a 3.5mm stereo phone jack. I was building this key for use with my QRPLabs QMX which has a great manual and a pinout for a keyer. Pretty simple, common is connected to the through-bolt on the tail end of the blade. DAH lead is connected to one of the front contact bolts, and DIT lead is connected to the other. I wasn’t too worried about keeping them straight as it was configurable in my keyer and I didn’t actually know how I was gong to hold the thing and use it!
The mono jack cable pass-through was handled by finding a rubber stopper of the about the right size, drilling a hole in the center of it, cutting a slit to pass the wire down to the hole and then gluing the stopper in place in the enclosure outlet.