On July 7th of this year I posted on qrptech@groups.io a message that I was in the mood for building a keyer and I asked for favorite circuits from everyone. No one mentioned the PMK Keyer from Midnight Design Solutions. While I was looking up keyer circuits I found this circuit design by Dave Benson K1SWL. I already had three Picos in stock in my junk box, so I went ahead and ordered the pcb along with some prototype boards and headers for experimenting with the Raspberry Pi Pico. George Heron N2APB kindly included a BOM to order all the parts from Mouser on his web site. That saved me a lot of time!
https://midnightdesignsolutions.com/pmk/
The hardest part of this build for me was getting the right female headers installed for the Pico on the PMK pcb. At first I used some headers from Adafruit, but they were not tall enough and the soldered male pin headers on the Pico were not going deep enough into the female headers. Luckily, I have a Hako FR-301 de-soldering gun and I was able to desolder the Adafruit female headers with no problem. Next time I will be more careful and do better planning! :)
Building the PMK keyer went smoothly and the only confusion I had was with the Setup mode and Operational mode of the keyer. I asked George some questions and he was able to give me the information I needed to understand how everything worked.
PMK discussion, news and support are available at https://groups.io/g/cwtd
This is a nice keyer and for me it was a easy build. The firmware is written in MMBasic and for me it is easier to understand than MicroPython. Using a terminal program called Tera Term to access the firmware and to Setup the keyer had a cool retro vibe!
I want to thank George and Dave for making this keyer available. Now I am motivated to see what other projects I can come up with using the Raspberry Pi Pico!
73,
Chaplain O. Alan Jones, USA Retired
N8WQ
