QRPguys.com used to sell a very inexpensive and serviceable single-lever paddle that mounted to the KX3 or KX2’s paddle mount. Unfortunately, that kit is no longer available. Fortunately, they still sell the PCB pieces that formed the infrastructure for the paddle. With a few parts, most of which may be in your junk box, you can make your own paddle.
It will require a few small machine screws and nuts, a $.72 connector (Digikey S5555-ND), and a springy blade. Instructions are on the QRPguys website. In addition, two guitar picks provide a finger piece that is an improvement over the rubbery sleeve that was part of the original kit.
The springy blade that makes up the lever and provides tension is the main challenge; most springy metal, like the hack saw blades we made keys from as kids, is difficult to drill, and two holes are needed to mount the blade. Someone suggested trying feeler blades that are used for automotive work, but I decided to try some thin dual copper-clad PCB.
Originally I planned to find some thinner-than-normal PCB, then drill a few holes next to the mounting point to lessen the stiffness at the pivot, as in the DIY dual panel I made from PCB years ago shown below.
DIY dual paddle from PCB
However, a local ham provided me with a piece of PCB that was so thin that I could cut it with a scissors. (I have not tried to local a commercial source of this.) This was so flexible that no weakening of the pivot point was necessary, but it was more flexible overall than ideal. I added a stiffener as described below.
I have another of these paddles with the original QRPguys blade and it is OK in its original form. However, because the blade is flexible along its length, it flexes where it meets the contacts, giving a softer “landing” than I like. I solved that by using two guitar picks as a finger piece and stiffener. That approach also worked well with the PCB lever. The following is a description of how I made the lever from PCB and guitar picks.
The original QRPguys blade is the same width for its length – about the width of a hacksaw blade. That works, but when my KX3 is tilted on its back feet, that puts the paddle lower than I would like. I wanted to raise the profile of the finger piece a bit and so I cut mine in the shape in the photo below.
PCB lever before drilling holes.
After drilling the mounting holes, I took two .96mm guitar picks and cut off the rounded tips. I positioned them so that this small end was near the mounting point, leaving a small bit of PCB exposed that would serve as the joint or pivot. I then drilled out holes in the picks so that the dit and dah contacts could go through the guitar picks to contact the PBC.
Lever and finger piece, left. On right are the "finger screws" to mount unit on rig.
Next step was to mount the PCB lever in place, positioning the guitar picks so that the contact screws would go through the holes (see top photo), then screw the contact points against the PCB to keep the picks in position for gluing. Finally, I glued the guitar picks in place, taking care that the screw contacts cleared the holes. When the glue was dried, I trimmed off any excess PCB around the guitar picks, installed the lever and adjusted the contacts.
From the side view you can see that the guitar picks tilt up slightly. That raised the finger pieces a bit, allowing higher access when the KX3 is tilted.
So that I could mount the paddle to the rig using my fingers rather than a screwdriver, I ran two screws through standoff spacers (see photos above). Just make sure that the screws don’t extend so far into the rig that they short out or damage something.
To me, the guitar picks feel much better than the rubbery surface of the original QRPguys finger piece and the paddle no longer has the springy feel that it had when the blade flexed at the contact points.
Update: The QRPGuys paddle, or something similar, is now available from https://qrpbuilder.com/kx_single_lever.
Comments