If the PIO pin could drive a fair amount of current at 3.3v into a long enough wire at that frequency you'd start to get into milliwatts, and AM radio is NOT a band that even amateur license operators can broadcast over a a certain power on. FCC part 15 dictates no more than a 3 meter antenna for personal devices at AM frequencies which is what does the power limiting essentially.
The harmonics fall off quick enough on such a setup that it wouldn't really be a problem - but the only way to really KNOW that is to have a real solid understanding of how this 'radio' you've just made is working, meaning how that square carrier wave is really being driven off the PIO pin, and thus you need the requisite EE knowledge and/or ham radio test equipment and experience.
I've seen more and more of these 'ChatGPT coded up a radio transmitter' posts and it kinda rubs me the wrong way. I'd like to see more calculations and disclaimers for people showing some responsibility with radio, and if it drives people to studying and taking an amateur radio license test that would be for the better...
Also a reasonably even bet that you already own a low-quality wall power supply that will produce more interference than anything you're going to be doing with a Pico and a 4" jumper wire (I've found a couple of offending devices in my house), but I'm certainly in no position to tell you if you should or shouldn't do something.
Without the proper knowledge or measurement equipment, I observed that the audio would fade out after a 30 cm distance. Combined with running it for mere seconds to test and record a demo, I assumed to be in the clear with the spirit of the regulations. Appreciate the reminder to be responsible with RF.
VHF and UFH are so deeply embedded in technology we almost forget it's there. It's fun to sweep for other peoples environmental sensors in your neighbourhood, even more fun to track and listen to satellites as they pass overhead.
https://www.digikey.com/en/maker/tutorials/2025/what-is-the-...
TEMLEST-LoRa (2025) 87.5m with LoRa over display cables
LoPHY (2024) 700m with LoRA
MAGNETO (2021) CPU-generated magnetic fields
"Rowhammer for qubits" describes hypothetically using electron tunneling and magnetically biased bit flips in standard RAM to simulate quantum operators.
I've heard stories of ham radio clubs teaching how to make a coaxial antenna out of coaxial cable (cable TV copper cable)
"Can you hotwire this computer to transmit a tone through the radio?" — Transformers (2007)
That's Teleco 101, basically the first lessons from a Teleco trade/vocational degree. And OFC known at any electrician degree.
What the fuck, that's crazy. For those similarly bewildered, look here [1].
[1] https://www.usenix.org/conference/usenixsecurity15/technical...
return (int64_t)(now_us - deadline_us) >= 0;
return now_us >= deadline_us;
return now_us > deadline_us;
The weirdly pedantic use of stdint.h types with unnecessary casting is another LLM-ism I see more and more. Passing int8_t to a function by value is really weird... and the second half of this conditional:
if (midi_note < 0 || midi_note > 127) {
None of this is a huge problem on it's own. But the cognitive cost of a million odd little things like this adds up really quickly across a large codebase when you're trying to debug something.
You'd want to use a spectrum analyzer to verify that other frequencies are present only at very low levels. TinySA might be the cheapest option or an used Digilent Analog Discovery.
Search for Tempest for Eliza.
Because the speaker is still slow, so if it got to it, there should be audio, but maybe the circuit filters out the PWM signal outright?
The PWM-based modulation is interesting, but as an amateur, I couldn't fully understand it or trust that the radio receiver reliably picks up the duty cycle as amplitude.
The fact that you are receiving it with an AM radio, doesn't mean that you are transmitting AM.
"A rose by any other name would smell as sweet" -- BillOr we could just use words that are useful for communicating things.