This is so bad, and dangerous. It outputs pwm from an unfiltered digital output, therefore generating a hell of harmonics on a wide set of frequencies, not just the one it's set to operate on. It can seriously jam not only broadcast FM transmission but also other services. Beware that airband is very close; any jamming on those frequencies can turn in huge fines if not landing the perpetrator straight to jail.
Want to test it? Fine, but never ever connect an antenna to it.
Turn Raspberry Pi’s GPIO into an FM Transmitter (2012)
11–20 of 89 posts
Re: Turn Raspberry Pi’s GPIO into an FM Transmitter (2012)
#12Earlier quoted context omitted.
Sigh, getting a amateur radio operator license is not difficult, and teaches people such wonderful concepts like avoiding interference with noisy transmitters. 1. If you are using a modulated square-wave without a filter, than the harmonics/overtones will be splattering the local spectrum. 2. Tools like KerberosSDR/KrakenSDR make triangulating illegal broadcasts rather trivial. 3. Keep in mind, some places have a $5k…
> Sigh, getting a amateur radio operator license is not difficult, It is if you are trying to run from someone who's liable to pluck your address out of a public database (like the one the FCC runs) and come after you, possibly with murderous intent. It is if the government persists in misgendering you because hating you is politically fashionable in some circles. I'm not arguing that it's conceptually difficult, but…
On a related note, I see a lot of amateur radio enthusiasts who use their call sign as a vanity license plate. If you do that you should be extra polite in traffic because if someone types that into Google they get your full name and address.
Re: Turn Raspberry Pi’s GPIO into an FM Transmitter (2012)
#13One needs to be careful with such home made devices as they may clash with the officially assigned frequencies. We had in France a similar story where a village was losing 3G/4G connectivity almost every day around 22:00. It seemed that there are interferences with something. A special car was sent by the national regulation entity, it was trying to triangulate the source. They found a house where the owner bought a…
Every mobile operator has stories like this. Back in the GSM times the common theme in Europe was people using illegaly imported devices made for the US market. The unlicensed 900 MHz band in the US fell right into the GSM band in Europe. Apparently the worst offenders were wireless security cameras.
Re: Turn Raspberry Pi’s GPIO into an FM Transmitter (2012)
#14If you want to build fully legal applications that transmit FM you can use the Si4713.
https://learn.adafruit.com/adafruit-si4713-fm-radio-transmit...
John Park did a short video on it https://www.youtube.com/watch?v=PKP6Z-cEbFQ
You can also buy a fully legal MP3 FM transmitter. https://radiofidelity.com/best-fm-transmitter-for-your-car/
Bitluni made a fun (illegal) AM radio transmitter with an esp32 https://youtu.be/lRXHd3HNzEo
Re: Turn Raspberry Pi’s GPIO into an FM Transmitter (2012)
#15Some notes about this setup. 1. The radio will kinda suck. You’re probably not doing it wrong. 2. The sanest way to get pifm to play a stream (say from modipy) is a FIFO. gstreamer will be your friend. 3. Music will sound like garbage without a high and low pass filter. 3.1 Volume becomes an issue, you’ll need to amplify quite a bit to match the volume of real radio stations so your ears don’t get blown out if it fli…
Sigh, getting a amateur radio operator license is not difficult, and teaches people such wonderful concepts like avoiding interference with noisy transmitters. 1. If you are using a modulated square-wave without a filter, than the harmonics/overtones will be splattering the local spectrum. 2. Tools like KerberosSDR/KrakenSDR make triangulating illegal broadcasts rather trivial. 3. Keep in mind, some places have a $5k…
That’s cool and all, but getting an amateur radio license would not have allowed me to do what I want legally anyway which is run a low power music FM station broadcasting to common radios in my own apartment. I do use a filter but it wouldn’t matter if I didn’t, I don’t really care that I’m splattering the spectrum when the broadcast doesn’t even make it through my walls.
Re: Turn Raspberry Pi’s GPIO into an FM Transmitter (2012)
#16Author here.
This code no longer works on new Pi's (it does a lot of low level very hardware stuff from userspace without a proper kernel driver). The code was written in a 24 hour Hackathon, so is very far from maintainable.
However there are other projects to do the same which do work on new Pi's.
There are ways to do a full software defined radio from a pi by using the I2S hardware, and that can transmit GPS, 433 MHz garage door openers, and various other things.
Obviously whatever you transmit you better be using some filters on the output if you want it to be vaguely legal.
Re: Turn Raspberry Pi’s GPIO into an FM Transmitter (2012)
#17Earlier quoted context omitted.
Sigh, getting a amateur radio operator license is not difficult, and teaches people such wonderful concepts like avoiding interference with noisy transmitters. 1. If you are using a modulated square-wave without a filter, than the harmonics/overtones will be splattering the local spectrum. 2. Tools like KerberosSDR/KrakenSDR make triangulating illegal broadcasts rather trivial. 3. Keep in mind, some places have a $5k…
> Sigh, getting a amateur radio operator license is not difficult, It is if you are trying to run from someone who's liable to pluck your address out of a public database (like the one the FCC runs) and come after you, possibly with murderous intent. It is if the government persists in misgendering you because hating you is politically fashionable in some circles. I'm not arguing that it's conceptually difficult, but…
Sounds like you should move someplace nicer, as many zones use a checkbox on the application to prevent publishing such details. ;)
Read about halfway through this book so far, and It argues a fairly good case that Mr. Burns was based on a real person: https://www.amazon.ca/When-McKinsey-Comes-Town-Consulting/dp...
Have a wonderful day, and have faith most are lazier than they are evil =)
Re: Turn Raspberry Pi’s GPIO into an FM Transmitter (2012)
#18This is so bad, and dangerous. It outputs pwm from an unfiltered digital output, therefore generating a hell of harmonics on a wide set of frequencies, not just the one it's set to operate on. It can seriously jam not only broadcast FM transmission but also other services. Beware that airband is very close; any jamming on those frequencies can turn in huge fines if not landing the perpetrator straight to jail. Want t…
It's a GPIO with the corresponding mA drive, it can not "seriously jam" anything. The hyperbole is ludicrous.
Re: Turn Raspberry Pi’s GPIO into an FM Transmitter (2012)
#19Earlier quoted context omitted.
Sigh, getting a amateur radio operator license is not difficult, and teaches people such wonderful concepts like avoiding interference with noisy transmitters. 1. If you are using a modulated square-wave without a filter, than the harmonics/overtones will be splattering the local spectrum. 2. Tools like KerberosSDR/KrakenSDR make triangulating illegal broadcasts rather trivial. 3. Keep in mind, some places have a $5k…
That’s cool and all, but getting an amateur radio license would not have allowed me to do what I want legally anyway which is run a low power music FM station broadcasting to common radios in my own apartment. I do use a filter but it wouldn’t matter if I didn’t, I don’t really care that I’m splattering the spectrum when the broadcast doesn’t even make it through my walls.
If I recall, license free 88.7MHz under 15mW transmitters for FM audio were very common in some zones.
Re: Turn Raspberry Pi’s GPIO into an FM Transmitter (2012)
#20This is so bad, and dangerous. It outputs pwm from an unfiltered digital output, therefore generating a hell of harmonics on a wide set of frequencies, not just the one it's set to operate on. It can seriously jam not only broadcast FM transmission but also other services. Beware that airband is very close; any jamming on those frequencies can turn in huge fines if not landing the perpetrator straight to jail. Want t…
It'd have to sit down and do some math, but I'm kinda skeptical that an FM Broadcast band harmonic would land on the air and right next to it.