N2EC Amateur Radio

Ed's Adventures in Amateur Radio

The N2EC Paddle Tamer (Project)

When I am operating CW from my home station I am usually using a K1EL K45 CW Modem as the keyer.  It has aptly been described as a “Swiss Army Knife of CW Keyers” as it is an incredibly capable device.  I have built and used some other keyers in the past, including the Hamgadgets Ultra Pico Keyer that works very well and I was quite pleased with.  The reason I decided to go for the K45 was that as someone who teaches multiple CW classes with the Long Island CW Club, I really need a visual indication of what speed I’m sending at as well as an easy way to be able to modify that speed in single word per minute increments.  The Pico Keyer will send its speed in CW after adjusting a potentiometer, but making those updates while teaching can be challenging.  I had been using my Yaesu FT-897 as a sidetone source for the classes (and still do), but that meant that I had to have a separate setup for teaching and operating other rigs.  The K45 has a LCD readout that allows you to see your speed (along with a whole lot of information) so it seemed like a good choice.

Of course, the K45 allows me to do iambic keying as you would expect. It also can act as a Winkeyer to allow for keying from the logging software of your choice for use in contests which was a plus as I was starting to get more interest in working contests.  Additionally, it provides a pleasant sidetone, which is helpful as my Hermes Lite 2, which I have been using a lot lately, does not generate sidetone when keying CW.  The K45 does a whole lot more than that though — and I don’t really even use the half of it.  It can key from a keyboard and has several keying memories for automation.  The keyboard also allows you to go deep into the menu system without needing a computer.  It can also do RTTY, HSCW, and QRSS.  It also has the ability to decode CW by sending your receive audio into the unit (I’ve never used that function, but it is there).  It also has a USB interface for use with the Winkeyer, the remote display application (which shows the LCD information on your computer), and to allow for firmware updates.  It is also very well designed and has ESD input protection and RFI suppression on all the connectors … which is a great thing, but is something which created an interesting problem for me.

I have a lot of different keys and paddles, and I love playing with different ones to keep my operations fun and interesting.  I have things setup so I can have multiple paddles feeding into the K45 via a splitter, then I have the output going into another splitter so that I can patch-in manual keys and bugs that feeds into a stereo jack switch that allows me to switch between multiple rigs while keeping them electrically isolated.  The end result is that I can easily switch between my favorite keys and paddles at a moment’s notice and route them to whatever rig I feel like using.  This all worked very well until I tried to connect my 9A5N Solid State Paddle to the K45. 

The 9A5N Paddle is a unique paddle that has no moving parts.  Instead of a standard contact closure when you touch the paddle it uses a series of strain gauge sensors to drive a microcontroller to provide the keying.  This provides some advantages.  You can set the force required to activate the key from 10 to 50 grams of force to your preference.  There are no contacts to get dirty and stick.  And the paddle is automatically “tight” as there is no gap at all to worry about.  It is a very nice bit of engineering.  But it appears to have a problem.

When I connected the 9A5N to my K45 it would cause the K45 to reboot itself and behave strangely.  It was very frustrating, as I wanted to be able to have it connected, but it just would not work.  I reached out to Steve K1EL over at K1EL Systems (the manufacturer of the K45) about what might be happening and right away he told me he was familiar with the issue.  It appears that the 9A5N paddle has some large transients that are generated as the microcontroller closes the switching transistors that allow it to work.  Those transients are large enough to overwhelm the input protection on the K45, which causes it to protect itself and exhibit the behavior I was seeing.  Steve was quite responsive and was willing to fully refund my purchase for the K45, or even remove the ESD protection for me if that was desired.  I had no desire to return it, and I’m a fan of ESD protection as I hope to use the K45 for many years, so I decided to just let it be and the 9A5N paddle went back on the shelf.

A little while later Steve reached back out to me and mentioned that another customer had come up with a solution to fix the issue by taking 33 ohm resistors in line with the tip and ring connections between the 9A5N and the K45.  The resistors were limiting those current spikes, and appeared to allow the two devices to work together as desired.  This seemed like a great idea, so I thanked him for following up and added it to my queue of projects.  Life got in the way as it always does and it sat on the list for a few months until just recently when I decided to build the device, 3D print an enclosure, and give it a try.  The result was what I’m calling the N2EC Paddle Tamer.

As mentioned, the circuit could not be simpler.  The box has two stereo 1/8 inch (3.5 mm) jacks on either side connected to a bit of perfboard with the tip and ring connections connected through separate 33 ohm resistors that I had in my supply.  The ground lead is just directly connected through between the sleeves of each connector.

I had some perfboard from Elegoo lying around that I had picked up for another project from Amazon while back, the resistors were also on hand, as were a couple of 1/8 inch (3.5 mm) stereo jack cables I had supplied for another project, so I didn’t need any parts.  All I needed was a box to put it all in, so I went into Fusion 360 and designed an enclosure to house the board and provide holes for the cables to enter and exit.  A quick print in PETG with my Bambu Labs X1 Carbon later, I had the box and was ready for assembly. After soldering the connections as per the schematic and tying a loop in the cables  to provide strain relief for the cable and connections, I closed up the snap-fit case I designed for it, complete with my call sign and the name of the device and gave it a test.

Happily, it worked perfectly.  Now the 9A5N Solid State Paddle was able to send crisply and accurately via the K45 and was able to coexist peacefully with the the rest of my keys and paddles.  It was a very simple project, but one that really has had an outsized impact on my CW operation.  The 9A5N is particularly good for QRQ (high-speed) operation, so I’m glad to have it available to me for all my rigs in the shack for those times when I feel like pushing my speed.  It is always fun when a project works well from the start and a few spare parts can make something work again.  Lots of fun.

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