[mk_stjames]

I want to point out that what keeps this 'OK' is that the little wire is so 'electrically short' compared to the actual wavelength at 1000khz (a real quarter wave antenna at that freq is like 75 meters)... and thus this limits the power of this 'transmitter' to probably nanowatts.

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...

[alnwlsn]

At least you are supposed to be allowed to transmit on AM (and FM) bands at very low power, at least under FCC rules. That's how they can sell those adapters for car radios. Some other ones you definitely are not supposed to use as far as I know, like the old analog TV signals - I've seen a couple of those sorts of projects recently. On the other hand, you can go and buy an illegal TV transmitter on Amazon right now.

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.

[pesfandiar]

Mea culpa.

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.

[ra]

If you're interested in this I definitely recommend you look into amateur radio licensing. I took mine a few years ago simply out of interest, and I learned so much from the advanced course.

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.

[cadr]

I don’t know what the regulations are in your country (looks like you are maybe in Canada?), but in many countries it is straightforward to get an amateur radio license, and then you can have all sorts of fun (under the rules).

[tl2do]

Transmitting on AM broadcast frequencies is generally prohibited unless it meets an extremely low-power exemption , even if you have amateur license(I have a Japanese amateur radio license). A practical way to reduce risk is to put a large resistor before the antenna so the radiated power stays within that exemption. You could start with 100 MΩ; if the receiver cannot pick it up, try 10 MΩ, and so on.

[userbinator]

A slightly less practical but more fun way is to do it on a ship in international waters. (Bringing a whole new meaning to "pirate radio"...)

[BoxOfRain]

There's still one example of a working offshore radio ship, the Ross Revenge in southern England which you can go and visit. She's one of the former Radio Caroline ships, the studios are still fired up every month for a weekend of broadcasting and they run tours. Radio Caroline themselves are still alive and kicking as a legal station broadcasting 24/7 online and on 648 AM; ironically the latter transmission comes from a former BBC World Service site. She wasn't really a 'pirate radio' ship as she was a Panamanian-flagged vessel in international waters so not subject to the Wireless Telegraphy Act in theory, but British citizens specifically would have committed an offence working on her in her free radio days. What really did Radio Caroline in as an offshore broadcaster was the Anglo-Dutch action against the clandestine organisation which supplied the ship, that and the move from a 3-mile to a 12-mile limit which forced her into more exposed waters.

Other than the RNI ship she was probably the best-equipped radio ship that ever put to sea, and certainly the strongest. She was a long-range trawler built for Arctic conditions, and the engineering which went into the radio station was really impressive; Peter Chicago her engineer by all rights should be up there with the greats in hacker lore. Most radio ships were clapped-out old vessels at the end of their lives, they were essentially slapped with transmitters and sent to sea to die since you can never take a radio ship back into port once it's broadcast. The Ross Revenge on the other hand was a very strong ship who was left purposeless midway through her life due to the Cod Wars. The generating and transmitting facilities were really sophisticated for radio pirates, there were plenty of redundancies and the ship could radiate multiple medium and short wave services.

The broadcast studios and accommodation are still active but most of the machinery spaces and the hull itself aren't in good condition. They've raised half a million pounds for repairs, but that's not actually all that much in the maritime conservation game. Hopefully it will be enough to stabilise the immediate problems with the hull and open a door to lottery funding though. If you're in the area I'd go and see her while you've definitely got the chance!

[Kim_Bruning]

You think you jest: https://en.wikipedia.org/wiki/Radio_Veronica .

A literal pirate ship!