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OP seems from India and AFAIK its illegal to transmit on FM frequencies without a license. I understand it might be low powered but theres a chance of Police co

OP seems from India and AFAIK its illegal to transmit on FM frequencies without a license. I understand it might be low powered but theres a chance of Police coming knocking on the door. Whats worse is it might interfere with emergency services. There is a reason we have spoctrum licences.

jacquesm 3y ago
Yes, technically it is illegal. But I've seen all kinds of gizmos that would inject a signal into the FM band to allow the use of car stereos that didn't have an 'aux' input. At those power levels the FCC isn't going to be bothered unless someone lodges a complaint, and even then they'll have a hard time finding the source unless they're practically standing on top of it. OP may want to turn down the radiated power until it just works for his MIL but no longer for the neighbors.
- jeswin 3y ago
  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.
  - jacquesm 3y ago
    At what levels of power was this? I suspect the OPs transmitter is hard to detect even at close (< 100 meters > 30 meters) range. Anything more powerful and you would definitely attract attention.
- mdip 3y ago
  > 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 https://en.wikipedia.org/wiki/TV_detector_van
  - mindcrime 3y ago
    [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. Heh. I drive a 2002 Chevy Suburban (don't laugh, I have a strong aversion to spending money on new vehicles) and it lacks an AUX input, so to this day I use one of those low-power FM transmitter adapters to pipe my phone's audio output to the vehicle stereo. They are amazingly handy little gadgets.
    - jonatron 3y ago
      When I had a cassette deck in my car, I added an AUX input by soldering a cable to a chip on the PCB, and running it out through the cassette slot.
      - schwartzworld 3y ago
        That's a product they sell. It looks like an audio cassette with an aux cord coming out of it. I used one for years in my old grand Marquis.
        jacquesm 3y ago
        That just wires the speaker output of the device to a set of coils sitting right in front of the tape playback head. GP did an end run around that by wiring straight into the trace in between the head pre-amp and the main amp.
- maxerickson 3y ago
  Technically, it's perfectly legal under FCC regulations. https://www.fcc.gov/media/radio/low-power-radio-general-information 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-releases-consultation-paper-issues-related-low-power-small-range-fm https://trai.gov.in/notifications/press-release/trai-release...
exitb 3y ago
It is Hacker News after all. And that's probably like jaywalking of RF violations. I'd be more afraid of the copyright people.
- acatton 3y ago
  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.
  - hasseldahoff 3y ago
    [flagged]
    - sigg3 3y ago
      No need to be rude. As someone who's worked in telecom for a number of years, the fines for broadcasting I've seen issued to individuals are insane. Not just radio but wireless amplification too. Different European country though. Always check the legislation in the country of operation. Emergency frequencies are held sacred by the powers that be.
      - hasseldahoff 3y ago
        [dead]
  - 6510 3y ago
    like the Indians said, you want to buy the sky too?
  - detaro 3y ago
    In Germany (like afaik all the EU), you can also freely buy and use small low-power FM transmitters for exactly the use case of sending your own music to radios...
Mistletoe 3y ago
If we ever have a world apocalypse and I’m alone, I know I can at least conjure one companion by suggesting I would use spectrum without a license and a ham enthusiast will appear.
- implements 3y ago
  <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.”
_thisdot 3y ago
Worth noting that there already exists a product in the Indian market by a big music label that addresses this exact issue. I’ve bought my grandfather one of those and he’s very happy with it!
- sriram_malhar 3y ago
  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.
gilbetron 3y ago
Illegal in India maybe. In the US: "In the United States, Part 15 of the U.S. Federal Communications Commission rules specifies that no license is needed if range of the transmitter does not exceed 200 feet (61 meters), although the Part 15 rules specify that the field strength should not exceed 250 µV/m (48db) at 3 meters" I haven't found the exact law in India, but looks like maybe it's legal for personal usage of FM provided power of transmitter is under 500 mW?
getwiththeprog 3y ago
Post a reference to the legislation or its not real
cptaj 3y ago
Its not that limited. Check out fm transmitters on amazon. https://www.amazon.com/s?k=fm+transmitter&ref=nb_sb_noss https://www.amazon.com/s?k=fm+transmitter&ref=nb_sb_noss This is what he means, not some bigger pirate radio situation
NelsonMinar 3y ago
Killjoy.
whinvik 3y ago
I don't know if you are from India but our laws are so complicated that I am sure every moment we are breaking one or the other. If we constantly worried about which ones we are breaking we would never get anything done!
sriram_malhar 3y ago
I know. It is illegal in most parts of the world. I'm taking over a commercial FM channel that my MIL won't listen to, and the transmitter has about a 20m radius. If the police come, I'll use the Constanza "Was that wrong?" defence. https://www.youtube.com/watch?v=-RvNS7JfcMM https://www.youtube.com/watch?v=-RvNS7JfcMM
- jacquesm 3y ago
  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.
  - ktzar 3y ago
    The FCC allows personal FM transmitters to operate with a maximum power output of 250 microvolts per meter at a distance of 3 meters. Other countries are more permissive, so this is not a problem. As long as you don't interfere with anyone and emit in a band that's not used in the area, it's perfectly fine.
    - vonseel 3y ago
      I was curious what kind of range that might have, so I put what you said into chatgpt and asked what the range of a typical car or home stereo would be, and it gave me this (not sure if it's correct). FWIW, much less than 20 miles, haha. -- The maximum power output of a personal FM transmitter allowed by the FCC is 250 microvolts per meter at a distance of 3 meters. The range of the transmitter depends on various factors such as terrain, obstructions, and interference. Assuming ideal conditions, such as no obstructions or interference, the range of the transmitter can be calculated using the inverse square law. This law states that the strength of a signal decreases with the square of the distance from the source. At a distance of 3 meters, the signal strength would be 250 microvolts per meter. At a distance of 6 meters, the signal strength would be 62.5 microvolts per meter (250/4). At a distance of 9 meters, the signal strength would be 27.8 microvolts per meter (250/9). Typical car and household stereos have a sensitivity of about 2 microvolts per meter. Using this sensitivity value, we can calculate the range of the transmitter for these devices. For a car stereo, the transmitter would have a range of about 26 meters (square root of 250/2). For a household stereo, the transmitter would have a range of about 63 meters (square root of 250/0.5). However, in reality, the actual range of the transmitter may be shorter due to various factors such as interference and obstructions.

jacquesm 3y ago

Yes, technically it is illegal. But I've seen all kinds of gizmos that would inject a signal into the FM band to allow the use of car stereos that didn't have an 'aux' input. At those power levels the FCC isn't going to be bothered unless someone lodges a complaint, and even then they'll have a hard time finding the source unless they're practically standing on top of it. OP may want to turn down the radiated power until it just works for his MIL but no longer for the neighbors.

jeswin 3y ago
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.
- jacquesm 3y ago
  At what levels of power was this? I suspect the OPs transmitter is hard to detect even at close (< 100 meters > 30 meters) range. Anything more powerful and you would definitely attract attention.
mdip 3y ago
> 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 https://en.wikipedia.org/wiki/TV_detector_van
- mindcrime 3y ago
  [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. Heh. I drive a 2002 Chevy Suburban (don't laugh, I have a strong aversion to spending money on new vehicles) and it lacks an AUX input, so to this day I use one of those low-power FM transmitter adapters to pipe my phone's audio output to the vehicle stereo. They are amazingly handy little gadgets.
  - jonatron 3y ago
    When I had a cassette deck in my car, I added an AUX input by soldering a cable to a chip on the PCB, and running it out through the cassette slot.
    - schwartzworld 3y ago
      That's a product they sell. It looks like an audio cassette with an aux cord coming out of it. I used one for years in my old grand Marquis.
      - jacquesm 3y ago
        That just wires the speaker output of the device to a set of coils sitting right in front of the tape playback head. GP did an end run around that by wiring straight into the trace in between the head pre-amp and the main amp.
maxerickson 3y ago
Technically, it's perfectly legal under FCC regulations. https://www.fcc.gov/media/radio/low-power-radio-general-information 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-releases-consultation-paper-issues-related-low-power-small-range-fm https://trai.gov.in/notifications/press-release/trai-release...

exitb 3y ago

It is Hacker News after all. And that's probably like jaywalking of RF violations. I'd be more afraid of the copyright people.

acatton 3y ago
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.
- hasseldahoff 3y ago
  [flagged]
  - sigg3 3y ago
    No need to be rude. As someone who's worked in telecom for a number of years, the fines for broadcasting I've seen issued to individuals are insane. Not just radio but wireless amplification too. Different European country though. Always check the legislation in the country of operation. Emergency frequencies are held sacred by the powers that be.
    - hasseldahoff 3y ago
      [dead]
- 6510 3y ago
  like the Indians said, you want to buy the sky too?
- detaro 3y ago
  In Germany (like afaik all the EU), you can also freely buy and use small low-power FM transmitters for exactly the use case of sending your own music to radios...

Mistletoe 3y ago

If we ever have a world apocalypse and I’m alone, I know I can at least conjure one companion by suggesting I would use spectrum without a license and a ham enthusiast will appear.

implements 3y ago
<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.”

_thisdot 3y ago

Worth noting that there already exists a product in the Indian market by a big music label that addresses this exact issue. I’ve bought my grandfather one of those and he’s very happy with it!

sriram_malhar 3y ago
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.

gilbetron 3y ago

Illegal in India maybe. In the US: "In the United States, Part 15 of the U.S. Federal Communications Commission rules specifies that no license is needed if range of the transmitter does not exceed 200 feet (61 meters), although the Part 15 rules specify that the field strength should not exceed 250 µV/m (48db) at 3 meters" I haven't found the exact law in India, but looks like maybe it's legal for personal usage of FM provided power of transmitter is under 500 mW?

getwiththeprog 3y ago

Post a reference to the legislation or its not real

cptaj 3y ago

Its not that limited. Check out fm transmitters on amazon. https://www.amazon.com/s?k=fm+transmitter&ref=nb_sb_noss https://www.amazon.com/s?k=fm+transmitter&ref=nb_sb_noss This is what he means, not some bigger pirate radio situation

NelsonMinar 3y ago

Killjoy.

whinvik 3y ago

I don't know if you are from India but our laws are so complicated that I am sure every moment we are breaking one or the other. If we constantly worried about which ones we are breaking we would never get anything done!

sriram_malhar 3y ago

I know. It is illegal in most parts of the world. I'm taking over a commercial FM channel that my MIL won't listen to, and the transmitter has about a 20m radius. If the police come, I'll use the Constanza "Was that wrong?" defence. https://www.youtube.com/watch?v=-RvNS7JfcMM https://www.youtube.com/watch?v=-RvNS7JfcMM

jacquesm 3y ago
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.
- ktzar 3y ago
  The FCC allows personal FM transmitters to operate with a maximum power output of 250 microvolts per meter at a distance of 3 meters. Other countries are more permissive, so this is not a problem. As long as you don't interfere with anyone and emit in a band that's not used in the area, it's perfectly fine.
  - vonseel 3y ago
    I was curious what kind of range that might have, so I put what you said into chatgpt and asked what the range of a typical car or home stereo would be, and it gave me this (not sure if it's correct). FWIW, much less than 20 miles, haha. -- The maximum power output of a personal FM transmitter allowed by the FCC is 250 microvolts per meter at a distance of 3 meters. The range of the transmitter depends on various factors such as terrain, obstructions, and interference. Assuming ideal conditions, such as no obstructions or interference, the range of the transmitter can be calculated using the inverse square law. This law states that the strength of a signal decreases with the square of the distance from the source. At a distance of 3 meters, the signal strength would be 250 microvolts per meter. At a distance of 6 meters, the signal strength would be 62.5 microvolts per meter (250/4). At a distance of 9 meters, the signal strength would be 27.8 microvolts per meter (250/9). Typical car and household stereos have a sensitivity of about 2 microvolts per meter. Using this sensitivity value, we can calculate the range of the transmitter for these devices. For a car stereo, the transmitter would have a range of about 26 meters (square root of 250/2). For a household stereo, the transmitter would have a range of about 63 meters (square root of 250/0.5). However, in reality, the actual range of the transmitter may be shorter due to various factors such as interference and obstructions.