Study for, and obtain, a ham radio licence.
Exactly what I was going to suggest!
I suggest building a transceiver in the 700 THz frequency range as parts are cheap and easily controlled by an Arduino. Antennae in that frequency range will be easy to miniaturize as well.
Were you able to recover it in the end, so to speak?
I'll look into it, I have an interest in the field so it would definitely be a good thing to gain experience with. Thank you for your advice!
Thank you! Do you mean 700kHz?
After some more research, it seems like a Nordic NRF24L01 transceiver could work? It has been used with an ATtiny85 in this instructable:
It operates at 1.9-3.6V which seems perfect for this project on paper. Does that seem like a good set of components to explore? I'd love to try them out on a breadboard and see if I can make it work
lol, no, that would take a 1/4 wave antenna the length of a football field. 700 THz.
That project looks reasonable, as long as you use 2xAA batteries to start.
Using the ATtiny85 will present some challenges (alternative Arduino core, programmer required).
Here is the deal if you are in the USA. Anyone can build an RF oscillator for any frequency as long as the RF output is in the microwatts region. Otherwise no one could experiment with any electronics.
The rub come in the receiver. A human cannot hear an RF carrier that just turns on and off when sending Morse code. Further processing is necessary to produce something that a human can hear.
So, my recommendation is to research and build RF oscillators and when you find a frequency with small enough components to fit yo needs, you are done. Be sure to use only miniature components, meaning SMT components where you can.
When you get the oscillator done and can hear it or see it sending code, begin on your receiver to match your oscillator.
When I was young, many such devices were available that worked on the regular AM broadcast band.
Good luck.
Clandestine one way morse code with a vibe. Hmmm, sounds like a setup for cheating at casino poker. Just what IS the intended use?
It's two way...
As @jremington has suggested, ATtiny85 might be a challenge for a first project.
Youâll want to consider exactly how you want the system to work before you start buying hardware. For example: How do you want to operate the transmitter? Do you want to âkeyâ it with a push button switch or some other way? Do you want to be able to use âcannedâ transmissions of common responses? Would some sort of visible or audible indicator of dots and dashes be handy? Will you transmit a tone to be heard at the receiver or some digital code that will trigger a buzzer at the receiver?
You can create and test most of that before you ever pick the âradioâ part of the project. I would consider getting a more mainstream Arduino that can be easily programmed in the IDE until you arrive at a final design.