Walkie-Talkie Keyer

I'm planning to visit 39C3. The ham radio community has an event named "Toilets on the Air" (TOTA) that takes place at the congress. Since I'm limited regarding luggage I will only carry a 2m/70cm walkie-talkie with me. But I'm doing mostly cw which means I have a problem: How to do cw using the walkie-talkie?

My first idea was to use a use a small sound generator, place it near the walkie-talkie, press PTT and key the beeper. While this might work, it is simply too complicated. So I searched the internet for a device that is able to control the walkie-talkie and generate morse code - and found the fm-keyer by Burkhard John (DK5JG). I liked the idea and decided to redesign it. The result is the Walkie-Talkie Keyer (beware: description is in German).

The device contains an AVR CPU which does the following:

• It contains a keyer for a paddle.
• It generates a side tone and plays it over the builtin speaker.
• It implements two CW memories for convenience.
• It controls the PTT line for the walkie-talkie, switches it into send mode for the first and after a short delay back into receive mode after the last character.
• And - important - it delays the morse code output to the walkie-talkie by a few hundred milliseconds (configurable) to allow it to activate the transmitter safely before the code is sent.

This is how it looks:

The Walkie-Talkie Keyer is configurable via morse commands when a paddle is connected. Simply press the <C> key, then key the command. Things that can be configured are the keyer speed, pitch, CW memories, transmit on and off delay and many other things. All settings are kept in permanent storage, so most things have only to be configured once.

The device does also support a straight key, but configuration is unavailable in this case.

A typical setup might look like this:

The mobile phone may be used as power supply for the Walkie-Talkie Keyer. The device connects to the mobile phone, a paddle and the walkie-talkie.

Schematics, a PCB design, the software, a printable case and some docs are available from Github. There are some minor problems with the first version of the PCB so I'm currently preparing an improved version.