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DIY Radio Tuna Tin "S" CW Transmitter Project

The December 2020 issue of QST p. 30 featured a do-it-yourself article entitled 'The Tuna Tin "S",' subtitled "A Bare-Bones Synthesized QRPp Transmitter". QRPp means the transmitted signal is less than 1 watt. Our "Elmers" will guide you in building this CW transmitter comprised of 2 circuits: a digital readout Si5351 frequency synthesizer that outputs a square wave into an IRF510 RF amplifier with a band pass filter that transmits an FCC-clean CW signal. Choose one of 3 bands: 80, 40 or 20 meters. Plug in a Morse key and a battery. Rotate a single knob to choose the displayed frequency. Depress the key and it transmits. Bare-bones is the operative word so that any club member should be able to build a working rig with assistance of virtual meeting attendees. For less than the cost of a book, a ham can build a working transmitter that can be heard on an existing receiver.

An Arduino Nano microcontroller is the brains of the rig executing 4 pages of software that can be modified to add new features. Our group building project will be conducted with Zoom meetings (the next one is pending schedule). Phil Sittner and Bob Mix have developed a kit that is better than Phil's working prototype.  The kit includes all the parts.  You just provide a low wattage soldering iron with a fine tip, 60/40 rosin core solder, solder wick, needle nose pliers, diagonal cutters, wire stripper, basic soldering skill and a desire to have fun.  You will need a computer to load the software to the Arduino Nano, and a multimeter and 50 ohm dummy load to test the completed unit.  There is no assembly manual, but we can probably guarantee your rig will work.  The 50 ohm dummy load can be as simple as a 50 ohm BNC terminator or two 1/2 watt or greater 100 ohm resistors (not wire wound) in parallel.

Our next DIY Radio Zoom meeting is scheduled for February 23 at 7:00 pm PST. 
Those who are merely curious are welcome to observe our Zoom build sessions.

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The Tuna Tin S Prototype Board Spectrum Analysis of Tuna Tin S Signal Spectrum Analysis of Tuna Tin S Signal

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Arduino Upload Procedure


  1. Prerequisite: computer with Internet access

  2. Download the IDE and install it from for your operating system

  3. Download Code Listing from for year 2020 month December

    • ARRL Members, log into your account

    • Navigate to

    • Select Issue Year 2020

    • Scroll down table to month of December

    • Download Code Listing for The Tuna Tin "S" - A Bare-Bones Synthesized QRPp Transmitter

  1. ARRL nonmembers can download the code from the DIYRadio Files folder

  2. Unzip the Code Listing ( into a folder on the desktop

  3. Create a folder inside that folder and call it TunaTinS

  4. Copy or drag TunaTinS.ino to the TunaTinS folder; this is the software sketch that will be uploaded

  5. Double-click TunaTinS in that folder to run the IDE

  6. Click Tools-Manage Libraries and enter adafruit; a list of Adafruit libraries will list

  7. Scroll down to Adafruit_SI5351 and click Install

  8. Scroll down to Adafruit_SSD1306 and click Install

  9. Click Close to exit the Library Manager

  10. Click on the checkmark icon (upper left under File) to compile

  11. To upload plug a Mini-USB cable into the Nano and the other end to a USB port on the computer

  12. Click Tools then Board then Nano

  13. Click Tools then Processor then ATMega328P; do NOT select ATMega328P (Old Bootloader)

  14. Click Tools-then Port then COM4; your port may be different

  15. Click Tools then Programmer then ArduinoISP; do NOT select Arduino as ISP

  16. Observe options in the lower right of the IDE window, for example:

    Arduino Nano, ATMega328P on COM4

  17. Click the Upload right-arrow icon (under Edit) and watch the LED's flash on the Nano

  18. In case of errors, click in the log in the bottom window, then enter Ctrl-A to highlight, Ctrl-C to copy, then Ctrl-V to paste into a DIYRadio New Topic message and send it

  19. Wilson used the Tool-Boards Manager to modify boards.txt; only the Arduino Nano needs to be listed. Please let Bob know if the Arduino Nano is not listed for you.

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