Comment by sriram_malhar

This has a range of around ten feet, so I think people are fine to tinker a bit.

A standard 3.3V GPIO can typically push something like 30 to 60 mW. You won’t get all of that as transmitted signal — it will depend on how well your random antenna wire matches the impedance of the gpio and the frequency. I’m really not sure the audio quality is going to be anything more than just intelligible, but I’d guess you’d get at least 10 mW or so of useful power, which means it should generally work within a small house.

No, I'm using this in my car just for a very short range (< 200mm)

Thanks for the link! I've enjoyed radio classics on satellite radio, so having an on-demand for specific genres is a welcome option.

All I could think of was the song Radio, Radio. See the line about cleaning up the nation.

https://genius.com/Elvis-costello-radio-radio-lyrics

Sorry, no dice. It isn't, at least not intentionally.

... I've always been amazed how often "Was that wrong?" works.

I guess I shouldn't be. Even letting them know you were fully aware you were breaking the law, most people would see its intended purpose -- to bring a little peace and comfort to a very old woman -- and have their own compassion kick in.

YMMV but I'm guessing you'd hear something along the lines of "Oh,... well,... (shuffles feet) ... just turn it off, then". Many of us have elderly people in our lives we wish we could provide some comfort to and most of us know we're headed there (if we're lucky to live that long). You know, assuming your 20m radius FM transmitter didn't, say, cause some cataclysmic event/knock emergency services offline for several city blocks, etc.

Put another way, while some police actually will pull you over and write you a ticket for going a couple of miles (km) per hour over the speed limit, most won't waste the brain power/physical energy/thermal paper to bother enforcing it.

I’ve had much better luck with 100% honesty. Just say you set up a 20m transmitter to improve the life of a 93 year old woman.

I bought a house in my very early 20s. Roommates of mine finished the third floor with no permits. Went to sell the house ten years later and the location it was in required a U&O inspection. My realtor told me to lie, apply for a permit and pretend I just did the work.

Instead I called the local building inspector and said, “Hello my name is xxx and I’m calling to confess.” He cracked up laughing, came to the house immediately to look at everything and told me I was fine.

Yeah no one will bother with such a low-powered device. I used an in-car bluetooth-to-FM tranmitter bought from Amazon India for years. They've been sold openly since forever. Like this one: https://www.amazon.in/Portronics-AUTO-10-Bluetooth-Car/dp/B0...

I hope they don't know how to use Google and if they do that that is a pseudonym you're posting under here or you might be in bigger trouble than you started with ;)

Anyway, cool to see you hack this, maybe try to tweak the power levels a bit so the neighbors don't have a reason to talk about it.

In the UK, if you break the law, they'll confiscate anything physically wired to it, computer included.

Where I live, this is absolutely not the jaywalking of RF violations. In Germany, if it is proven that your signal was potentially interfering with emergency services, you will be liable for any damage to victims in civil courts. And if somebody dies in your area because the emergency services couldn't get there on time, you will be criminally charged for "negligent manslaughter."

I wouldn't play at all with non-approved RF frequencies personally.

Technically, it's perfectly legal under FCC regulations.

https://www.fcc.gov/media/radio/low-power-radio-general-info...

Looks like India doesn't permit it, but is looking at doing so (at least, for some purposes):

https://trai.gov.in/notifications/press-release/trai-release...

  > Yes, *technically* it is illegal.

Oh how many phrases start "Yes, technically" in my life.

The law is an interesting beast. I know nothing about the law in India as it relates to FM band transmitters but I suspect that the law predates the common availability of adapters that one might use in ones car to add an input to a stereo that lacks such a highly technical circular hole for such purposes[0]. Once these devices gained wide adoption due to both their utility and -- more generally -- the fact that operating one is usually so benign that they can be difficult to discover let alone actually cause enough interference to warrant them to be seized.

The intention of the law was to prevent someone from operating a pirate radio station/give exclusivity to a single license-holder for that frequency. Since these devices don't violate the spirit of the law, the governing body finds it easier to carve out an informal exemption rather than explicitly write one in. It can also be tricky to correct a law that has a very valid reason for existing but may have cases where total enforcement isn't realistic[1].

The law may not have caught up to the reality on the ground and the legislatures answer to it is "enforce it when the interference is enough that someone notices." One might imagine a world where something akin to TV Detector-like Vans[2] drape the country-side in a dragnet to catch all of those pirate FM-input-devices but that usually only happens if there's a substantial amount of tax revenue to be gained ... to pay for the vans.

[0] I had one of these in the 90s (in the US, where it's not illegal if designed correctly) that connected my Discman to my ridiculously sad factory radio which lacked both external input and even a cassette deck.

[1] I do very little with regard to radio communication (if that isn't obvious) but I'd imagine most lawmakers do even less, so now you have to bring in experts to figure out "what's an acceptable amount of interference in this specific use case" and "how should a device like this be restricted." Not that government isn't famous for wildly wasting money or anything but I'd imagine the thinking is that it's not worth the effort to correct.

[2] https://en.wikipedia.org/wiki/TV_detector_van

But quaintdev is right in that Indian Police for some reason takes this somewhat seriously. For highway patrol, I suspect it's boredom and this gives them something to chase. I remember in the late 90s when I was in college, the police showed up a couple of times when students were transmitting from one of the hostels. They'd let it go, but they did show up.

<Dusts off Ham Licence> Anyone can use amateur frequencies in a genuine “no other communication options available” emergency, if I remember the regulations correctly.

Edit: “§ 97.403 Safety of life and protection of property. No provision of these rules prevents the use by an amateur station of any means of radio communication at its disposal to provide essential communication needs in connection with the immediate safety of human life and immediate protection of property when normal communication systems are not available.”

Do you mean the saregama Caravaan? If so, I bought her one of those and it just didn't cut the mustard.

The built-in collection either didn't have songs that she liked (from the '40s), or they weren't clustered together, or were mixed up with other songs.

I could load a flash disk with her playlist to plug into that player, but it wouldn't know what to play at what time (calm songs in the early and late hours, peppier numbers on other days, festival specific numbers on some days). This was a big deal. I can even change the playlist from elsewhere (a script automatically mirrors the playlist that I maintain on a server)

Bluetooth streaming is possible with the device, but not an option for my MIL ... that would require her to learn to use a cellphone.

I’ve wanted to try something like this with a Pi or something else running Linux. Is mpd a good choice for that scenario? Does it support being able to use custom events eg a button on the gpio for play/pause?

Several homes in my city put up holiday lights that are synced to music and transmitted over FM. The signal only works if you’re parked near the house.

Cool! I asked because there are many niche playlists on Spotify you can find for oldies, for example some very specific for the 60s, 50s, 40s, etc. Perhaps it could help her discover similar, but new, music.

They all sound out of breath. Not sure what causes that effect/perception. Listening to it again, it seems like the plosives (like d, or t) have no pop like there was no air pressure behind them.

Ha, that’s awesome. Several of the voices sounded just right for radio. I see the lib is limited to 24khz, maybe why it has an almost AM radio sound?

> You can turn the RPi itself into an FM transmitter.

Never tried it, but given the way it works, you definitely need some output filtering unless you accept to pollute all harmonics of your channel (which might be licensed spectrum too, and interfere with services you don't want to interfere with in the first point)

You do still need that. The broadcast from gpio thing is very low quality and produces square waves which interfere with everything