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Thanks! Say I wanted to transmit, what’s the general process for navigating the minefield? One of the things I’d like to do is build a software-defined radio (

Thanks! Say I wanted to transmit, what’s the general process for navigating the minefield? One of the things I’d like to do is build a software-defined radio (using an rpi, for example) and use it to send something like Ethernet packets over the air.

HWR_14 5y ago
> what’s the general process for navigating the minefield? Let me start with, I am very ignorant of the pitfalls. If you can get a HAM license, they will teach you all the rules and you'll get to play in more RF space. Otherwise, if you limit your transmissions to the WiFi bands at 1mWatt or less, you'll be fine (those are open). However, it is very difficult to do well because you are likely to generate noise on a band you are not trying to transmit on. Then the FCC will get mad at you, because you are responsible for all transmissions. Step into the wrong frequency range and you're looking at a 5 figure fine. If you just want to play with radio hardware, so are a few other bands like 433Mhz where you can buy transmitter/receiver boards that the manufacturer certifies will not transmit outside freq. range. That's tested, so they should work well and you won't get in trouble with the FCC (the manufacturer limits the boards), the manufacturer would.
- omginternets 5y ago
  Realistically, how likely is one to get caught for such "leaky" transmissions, assuming one is not continuously broadcasting? It's not that I intend to do it -- I'm trying to get a bead on the extent to which this is playing with fire. Your point about the HAM license is well-taken. That's probably a sensible next step.
  - HWR_14 5y ago
    You're rapidly leaving the limits of my knowledge, so going forward this is based on half-remembered things told to me. Huge grain of salt time. I believe "leaky" transmissions are a result of the circuit design/construction (which could also be exacerbated or mitigated at the antenna level) and power being sent through the circuit and are not dependent on continuous/sporadic broadcasting. It may make it less likely to get caught, as triangulation requires an active signal. But if you bleed into ranges people care about (say HAM operators or police/military/aviation) the resources devoted to stopping you might get impressive (HAM operators because it's their hobby, the others have real government resources). Keep in mind, leaking isn't just illegal, it's also annoying whoever's transmission range you are leaking into. Again, I would lean towards a $10 433Mhz board or a $20 ~900MHz board shipped from any electronics manufacturer before I started building my own transmitters. Or, if you're interested in transmitting using SDR and have ~$350 look into the HackRF or LimeSDR. AFAIK, they aren't FCC certified, but the HackRF in particular seems to have a wide amount of open-source use already and is probably safer than rolling your own.
    - omginternets 5y ago
      This is very helpful. Thanks for taking the time to answer :)

HWR_14 5y ago

> what’s the general process for navigating the minefield? Let me start with, I am very ignorant of the pitfalls. If you can get a HAM license, they will teach you all the rules and you'll get to play in more RF space. Otherwise, if you limit your transmissions to the WiFi bands at 1mWatt or less, you'll be fine (those are open). However, it is very difficult to do well because you are likely to generate noise on a band you are not trying to transmit on. Then the FCC will get mad at you, because you are responsible for all transmissions. Step into the wrong frequency range and you're looking at a 5 figure fine. If you just want to play with radio hardware, so are a few other bands like 433Mhz where you can buy transmitter/receiver boards that the manufacturer certifies will not transmit outside freq. range. That's tested, so they should work well and you won't get in trouble with the FCC (the manufacturer limits the boards), the manufacturer would.

omginternets 5y ago
Realistically, how likely is one to get caught for such "leaky" transmissions, assuming one is not continuously broadcasting? It's not that I intend to do it -- I'm trying to get a bead on the extent to which this is playing with fire. Your point about the HAM license is well-taken. That's probably a sensible next step.
- HWR_14 5y ago
  You're rapidly leaving the limits of my knowledge, so going forward this is based on half-remembered things told to me. Huge grain of salt time. I believe "leaky" transmissions are a result of the circuit design/construction (which could also be exacerbated or mitigated at the antenna level) and power being sent through the circuit and are not dependent on continuous/sporadic broadcasting. It may make it less likely to get caught, as triangulation requires an active signal. But if you bleed into ranges people care about (say HAM operators or police/military/aviation) the resources devoted to stopping you might get impressive (HAM operators because it's their hobby, the others have real government resources). Keep in mind, leaking isn't just illegal, it's also annoying whoever's transmission range you are leaking into. Again, I would lean towards a $10 433Mhz board or a $20 ~900MHz board shipped from any electronics manufacturer before I started building my own transmitters. Or, if you're interested in transmitting using SDR and have ~$350 look into the HackRF or LimeSDR. AFAIK, they aren't FCC certified, but the HackRF in particular seems to have a wide amount of open-source use already and is probably safer than rolling your own.
  - omginternets 5y ago
    This is very helpful. Thanks for taking the time to answer :)