6 ms·

Is 2.4GHz truly unlicensed? Could I emit 500W or more with whatever modulation or lack thereof and not be prosecuted?

NovemberWhiskey 5y ago
No; in the US, for example, Part 15 devices are, I think, limited to a maximum of 1W transmitted power at 2.4GHz, and 4W of EIRP (effective isotropic radiated power). i.e. maximum antenna gain of 6dBi at full power. For fixed, point-to-point installations there is a special rule in effect: you can get more EIRP by having higher gain antennas as long as you back off the power; e.g. you can drop down to 22dBm (159mW) but have a 30dBi antenna and get 52dBm (159W) of EIRP. A 30dBi antenna at 2.4GHz is, by the way, something like a 1.5 meter diameter parabolic grid.
- 8bitsrule 5y ago
  Power levels can depend on the service and region. For an example in the US, this Wikipedia page outlines part 15 fairly completely, and links to most types of services with more details: https://en.wikipedia.org/wiki/Title_47_CFR_Part_15 https://en.wikipedia.org/wiki/Title_47_CFR_Part_15 E.g. I followed the link to '802.11 wireless LANs', thence to to '2.4_GHz_radio_use' where I was surprised to learn that US 'Amateur Radio operators can transmit [video&audio] ... in the 2.4 GHz band—and all ISM frequencies above 902 MHz—with maximum power of 1500 watts.'
  - sbierwagen 5y ago
    Back in the day Ubiquiti used to sell a bunch of radio modules that let you transmit on the ham or public safety bands using their wifi equipment. Presumably they also had firmware that implemented the other limits. (Ham transmissions can't be encrypted and must include your callsign)
  - NovemberWhiskey 5y ago
    Right; however that's a licensed form of usage - 802.11g channels 1 through 6 are all entirely within the 13cm amateur band in the U.S.
    - bagansio 5y ago
      That's incredible
- red0point 5y ago
  Any idea where to get a good quality 30dBi antenna these days (for 2.4GHz or different frequencies)?
  - avidiax 5y ago
    https://mikrotik.com/products/group/antennas https://mikrotik.com/products/group/antennas But that's 5GHz or 60Ghz.
jcrawfordor 5y ago
2.4GHz is unlicensed, but through a few different routes FCC regulations prohibit operating, distributing, marketing, etc an intentional radiator (and many types of unintentional/incidental radiators) without an equipment authorization or device certification. So the pedantic answer is that you can do whatever you want in 2.4GHz but you can't do it using whatever device you want, which creates limitations of generally 1W as sort of the simplest answer.
nullc 5y ago
> Could I emit 500W or more with whatever modulation or lack thereof and not be prosecuted You could emit 500w in the 2.4GHz ISM band legally as a ham radio operator, as there is an overlapping ham allocation, so long as you complied with the ham requirements (which limits you somewhat on the 'whatever modulation' front). But why would you? You're limited to line of sight communications -- far less than 500w will get you to the horizon. :P The only application I can think of for 500w at 2.4GHz would be moon-bounce. :) Outside of the ham radio overlap, any intentional transmission in that band would have to be via a type-certified device. ... So it's more a question of what devices the fcc will certify than what you're able to do.
- H8crilA 5y ago
  Thanks for the answer (also thanks for the sibling answers), I will only add one thing: why: I would like to realize a dream and build my own somewhat okay radar. At some point, I'm very far away from that :). And I am definitely not going to endlessly ruin every neighbor's WiFi even if it's legal.
- h2odragon 5y ago
  > why would you? Combination hunting rifle and microwave oven: cook your ducks on the wing! I suspect it would take unfeasible amounts of power to pull off in reality. Pesky humidity.
Johnythree 5y ago
"Unlicensed" does not mean "Unregulated". There are still type-approval requirements for almost all transmitters (except Amateur radio where the responsibility falls on the licensed operator, rather than the actual equipment).

No; in the US, for example, Part 15 devices are, I think, limited to a maximum of 1W transmitted power at 2.4GHz, and 4W of EIRP (effective isotropic radiated power). i.e. maximum antenna gain of 6dBi at full power. For fixed, point-to-point installations there is a special rule in effect: you can get more EIRP by having higher gain antennas as long as you back off the power; e.g. you can drop down to 22dBm (159mW) but have a 30dBi antenna and get 52dBm (159W) of EIRP. A 30dBi antenna at 2.4GHz is, by the way, something like a 1.5 meter diameter parabolic grid.

8bitsrule 5y ago
Power levels can depend on the service and region. For an example in the US, this Wikipedia page outlines part 15 fairly completely, and links to most types of services with more details: https://en.wikipedia.org/wiki/Title_47_CFR_Part_15 https://en.wikipedia.org/wiki/Title_47_CFR_Part_15 E.g. I followed the link to '802.11 wireless LANs', thence to to '2.4_GHz_radio_use' where I was surprised to learn that US 'Amateur Radio operators can transmit [video&audio] ... in the 2.4 GHz band—and all ISM frequencies above 902 MHz—with maximum power of 1500 watts.'
- sbierwagen 5y ago
  Back in the day Ubiquiti used to sell a bunch of radio modules that let you transmit on the ham or public safety bands using their wifi equipment. Presumably they also had firmware that implemented the other limits. (Ham transmissions can't be encrypted and must include your callsign)
- NovemberWhiskey 5y ago
  Right; however that's a licensed form of usage - 802.11g channels 1 through 6 are all entirely within the 13cm amateur band in the U.S.
  - bagansio 5y ago
    That's incredible
red0point 5y ago
Any idea where to get a good quality 30dBi antenna these days (for 2.4GHz or different frequencies)?
- avidiax 5y ago
  https://mikrotik.com/products/group/antennas https://mikrotik.com/products/group/antennas But that's 5GHz or 60Ghz.

jcrawfordor 5y ago

2.4GHz is unlicensed, but through a few different routes FCC regulations prohibit operating, distributing, marketing, etc an intentional radiator (and many types of unintentional/incidental radiators) without an equipment authorization or device certification. So the pedantic answer is that you can do whatever you want in 2.4GHz but you can't do it using whatever device you want, which creates limitations of generally 1W as sort of the simplest answer.

nullc 5y ago

> Could I emit 500W or more with whatever modulation or lack thereof and not be prosecuted You could emit 500w in the 2.4GHz ISM band legally as a ham radio operator, as there is an overlapping ham allocation, so long as you complied with the ham requirements (which limits you somewhat on the 'whatever modulation' front). But why would you? You're limited to line of sight communications -- far less than 500w will get you to the horizon. :P The only application I can think of for 500w at 2.4GHz would be moon-bounce. :) Outside of the ham radio overlap, any intentional transmission in that band would have to be via a type-certified device. ... So it's more a question of what devices the fcc will certify than what you're able to do.

H8crilA 5y ago
Thanks for the answer (also thanks for the sibling answers), I will only add one thing: why: I would like to realize a dream and build my own somewhat okay radar. At some point, I'm very far away from that :). And I am definitely not going to endlessly ruin every neighbor's WiFi even if it's legal.
h2odragon 5y ago
> why would you? Combination hunting rifle and microwave oven: cook your ducks on the wing! I suspect it would take unfeasible amounts of power to pull off in reality. Pesky humidity.

Johnythree 5y ago

"Unlicensed" does not mean "Unregulated". There are still type-approval requirements for almost all transmitters (except Amateur radio where the responsibility falls on the licensed operator, rather than the actual equipment).