5 ms·

Unlicensed Radio

78 points by zdw 5y ago

akira2501 5y ago
> Because the ISM bands were basically reserved to be a no-man's land that non-communications devices could freely emit into, there are no licensing requirements for ISM emissions. Just because there are no formal licensing requirements does not mean that an implied license doesn't exist, nor does it mean that there are no rules. The ISM bands have for a very long time had both transmitter and antenna power limits attached to them. What I think is missing in this article is an understanding that all RF spectrum belongs to the public. The FCC does not own it, it licenses parts of it for coordination so that the spectrum is _usable_ by the public at large. They operate the spectrum on _behalf_ of the public, and their decisions and procedures are based entirely around this concept.
- jcrawfordor 5y ago
  Yes, the limitations are due to device certification under part 15. However, this is in no way an implied license, as "license" has specific meaning within the context of various parts of the FCC regulations. Part 15 covers unlicensed radiators, so essentially "licensed" and "part 15" are antonyms. This is most significant in that licensing almost always implies some degree of protection from interference (although it may be rather limited), while part 15 devices receive no such protection... when someone interferes with your WiFi, you cannot complain to the FCC (there's some recourse related to the legality of devices, but you cannot for example seek a license modification to address the interference as licensed users generally can to some degree). The existence of "soft licensed" services such as the part 95 services somewhat complicates this as there are services like family radio service (part 95B) that are "licensed by rule," meaning that there is an implicit license, but that somewhat illustrates the point: part 95B radios like the common consumer Motorolas and Midlands are implicitly licensed, WiFi is not! FRS has (limited) regulatory protection from interference, WiFi does not. FRS has limitations on nature of usage, Part 15 has none, but the device must be certified to meet part 15 specs for emissions. The whole "part 15" thing gets more into device certification, which I mentioned in the post I will discuss in the future as it's a topic all of its own. The history of part 15 device certification is closely related to the history of the ISM bands in some ways, but they are not 1:1, as part 15 covers both unintentional/incidental radiators (essentially all electronic devices) as well as intentional radiators which do not have a license... microwave ovens and WiFi are the quintessential examples of the latter. It is of course obvious that RF spectrum belongs to the public, but in the US it is regulated by both the FCC and the NTIA depending on the user and the importance of the ITU cannot be understated as many of these services have at least partial international coordination. Certain radio licenses in the US will also require the approval of either Industry Canada or Mexico's IFT, although this is required under FCC regulations some of which implement treaty obligations. That said, I live in the US and am not a radio technician in the federal government (which is generally exempt from FCC regulations), so I tend to stick to what I know best: 47 CFR! It's also important to understand that in most cases the FCC does not coordinate spectrum usage on a level more granular than services and instead leaves it to other government agencies or private organizations, within the scope of each service. Part 90 is an interesting example, which is FCC licensed on a frequency level but coordinated by private companies for profit (the FCC just approves whatever frequency the private frequency coordinator recommends). I'll probably write on this in the future.
- GekkePrutser 5y ago
  In Europe there's not only power limitations but also duty cycle on some bands. Eg on 868Mhz you can only transmit 1% of the time. I don't think the equivalent US band of 915Mhz has this, and it has a much higher maximum power which is really nice. Wish we had something like this here.
  - vvanders 5y ago
    Yep, you can see this if you go poke into LoRa and associated protocols. 915MHz does have some restrictions on either using spread spectrum, frequency hopping or much lower power limits so it's still quite different than say the ham bands.
  - Terry_Roll 5y ago
    Yes the Europeans give away some of their knowledge when looking at radio spectrums, the recent 5G bands causing problems with aircraft at airports in the US is one such example of forward planning or lack of.
  - CraigJPerry 5y ago
    There’s also listen-before-talk rules for devices in certain ISM bands in the EU. Affects at least LTE, Wifi and a few other users in 5.8ghz
  - usrn 5y ago
    Our band around 400Mhz has a similar limitation.
- h2odragon 5y ago
  > all RF spectrum belongs to the public. The FCC does not own it, I wish the FCC and more radio enthusiasts also understood that. Its amazing how many epochal inventions in radio have come to the public through getting around the FCC one way or another.
  - charcircuit 5y ago
    Not just inventions in radio. Pretty much all electronics nowadays are at least unintentional radiators.
karteum 5y ago
For people interested in regulation in EU/CEPT area, unlicensed bands (ISM and SRD) are captured in ERC 70-03, where you can see the bands and associated limitations (in terms of EIRP, Duty-Cyle, and other things) https://docdb.cept.org/download/25c41779-cd6e/Rec7003e.pdf https://docdb.cept.org/download/25c41779-cd6e/Rec7003e.pdf Annex 1 is about generic SRD. The other annexes are about other bands and/or more favourable conditions for specific applications. This may seem complex and over-regulated, but there is a good reason for that : - CEPT cares that all applications get a fair chance to access the spectrum (not just "the technology which emits the strongest signal") : for example, all Wi-SUN equipments (APs, relays and end nodes) can emit up to 500 mW (with power-control) while Lora end nodes have a 25 mW transmit power. Technical studies and simulations have shown that Lora (and siblings) would not survive if wi-sun was going to be widely deployed, and this is one reason why some parts of the bands for networked SRD have a 25 mW limitation while other parts are less constrained. - those "additional opportunities" in other annexes are made based on dedicated technical studies (to check the impact on adjacent bands/services) that do a lot of assumptions with regards to potential/future densities of devices (because what matters if often the aggregated interference, not just the one from a single device)
H8crilA 5y ago
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.
nullc 5y ago
> Twitter.com still takes 10 seconds to render 140 characters of text, but it's getting that text at the better part of a gigabit per second! Assuming your phone is laying on top of the access point. :P Some of the distances for higher speeds are so short that I wonder if we need new terms for 'wireless' (there is no wire) vs 'untethered' (you're not stuck at a specific location).
drmpeg 5y ago
> There's good news: 5GHz is not an ISM band. Part of the band is ISM. 5725 to 5875 MHz. https://www.ecfr.gov/current/title-47/chapter-I/subchapter-A/part-18/subpart-C/section-18.301 https://www.ecfr.gov/current/title-47/chapter-I/subchapter-A...
- usrn 5y ago
  Much of 5ghz also requires DFS which can be a pain.
alhirzel 5y ago
I love this writing style, does anyone know of similar authors?
usrn 5y ago
I've always felt like carving up the digital spectrum more specifically than just giving it to different use cases (HAM, commercial, consumer etc) is harmful. Modern digital modes can transmit over each other on the same frequency and still get the message through, they're effectively self regulating.
ranger207 5y ago
> Everyone grumbles about Baofeng people, but I've had some contact with rural police and fire departments and you would be amazed at the things their "radio technician" (chief's nephew) thinks are a good idea. @jcrawfordor, what kind of bad ideas have you heard of here?
- Animats 5y ago
  He's talking about these: [1] They're cheap VHF FM analog handheld radios. Prices start around US$30. They can emit on the 462 MHz and 467 MHz Family Radio Service and General Mobile Radio Service bands, usable by anyone in the US and. That's fine. They can also emit in amateur radio bands, at higher power (8 watts claimed), which requires a ham license. The device controls do not make much of a distinction between the two modes. They're often used in the ham bands by non-hams, mostly preppers, hunters, militias, and people who own too much camo. This annoys radio hams. [1] https://baofengradio.us/ https://baofengradio.us/
  - sbierwagen 5y ago
    GMRS is not unlicensed. A license currently costs $70, is good for ten years, and can only be used by you and your immediate family. Baofengs are not type certified for FRS or GMRS, since their transmission power is too high and the antennas are not permanently attached. It is illegal to use them on those frequencies, even if you have a ham or GMRS license, though enforcement is nonexistent.
  - fortran77 5y ago
    It's not legal to use a Baofeng on GMRS and FRS because they're not "type accepted" for this purpose though there's little chance you'll get caught.
  - usrn 5y ago
    They're specifically for HAMs. You should not be transmitting on FRS with those even if the software lets you do it, that's why there's no distinction: the user is expected to know what they're doing. RE: Preppers Most of the preppers I know that bother with these get their HAM license (They usually get General class actually, so they can use HF.) Maybe you live near some poorly behaved nut cases but I have yet to meet those.

78 points by zdw 5y ago

> Because the ISM bands were basically reserved to be a no-man's land that non-communications devices could freely emit into, there are no licensing requirements for ISM emissions. Just because there are no formal licensing requirements does not mean that an implied license doesn't exist, nor does it mean that there are no rules. The ISM bands have for a very long time had both transmitter and antenna power limits attached to them. What I think is missing in this article is an understanding that all RF spectrum belongs to the public. The FCC does not own it, it licenses parts of it for coordination so that the spectrum is _usable_ by the public at large. They operate the spectrum on _behalf_ of the public, and their decisions and procedures are based entirely around this concept.

jcrawfordor 5y ago
Yes, the limitations are due to device certification under part 15. However, this is in no way an implied license, as "license" has specific meaning within the context of various parts of the FCC regulations. Part 15 covers unlicensed radiators, so essentially "licensed" and "part 15" are antonyms. This is most significant in that licensing almost always implies some degree of protection from interference (although it may be rather limited), while part 15 devices receive no such protection... when someone interferes with your WiFi, you cannot complain to the FCC (there's some recourse related to the legality of devices, but you cannot for example seek a license modification to address the interference as licensed users generally can to some degree). The existence of "soft licensed" services such as the part 95 services somewhat complicates this as there are services like family radio service (part 95B) that are "licensed by rule," meaning that there is an implicit license, but that somewhat illustrates the point: part 95B radios like the common consumer Motorolas and Midlands are implicitly licensed, WiFi is not! FRS has (limited) regulatory protection from interference, WiFi does not. FRS has limitations on nature of usage, Part 15 has none, but the device must be certified to meet part 15 specs for emissions. The whole "part 15" thing gets more into device certification, which I mentioned in the post I will discuss in the future as it's a topic all of its own. The history of part 15 device certification is closely related to the history of the ISM bands in some ways, but they are not 1:1, as part 15 covers both unintentional/incidental radiators (essentially all electronic devices) as well as intentional radiators which do not have a license... microwave ovens and WiFi are the quintessential examples of the latter. It is of course obvious that RF spectrum belongs to the public, but in the US it is regulated by both the FCC and the NTIA depending on the user and the importance of the ITU cannot be understated as many of these services have at least partial international coordination. Certain radio licenses in the US will also require the approval of either Industry Canada or Mexico's IFT, although this is required under FCC regulations some of which implement treaty obligations. That said, I live in the US and am not a radio technician in the federal government (which is generally exempt from FCC regulations), so I tend to stick to what I know best: 47 CFR! It's also important to understand that in most cases the FCC does not coordinate spectrum usage on a level more granular than services and instead leaves it to other government agencies or private organizations, within the scope of each service. Part 90 is an interesting example, which is FCC licensed on a frequency level but coordinated by private companies for profit (the FCC just approves whatever frequency the private frequency coordinator recommends). I'll probably write on this in the future.
GekkePrutser 5y ago
In Europe there's not only power limitations but also duty cycle on some bands. Eg on 868Mhz you can only transmit 1% of the time. I don't think the equivalent US band of 915Mhz has this, and it has a much higher maximum power which is really nice. Wish we had something like this here.
- vvanders 5y ago
  Yep, you can see this if you go poke into LoRa and associated protocols. 915MHz does have some restrictions on either using spread spectrum, frequency hopping or much lower power limits so it's still quite different than say the ham bands.
- Terry_Roll 5y ago
  Yes the Europeans give away some of their knowledge when looking at radio spectrums, the recent 5G bands causing problems with aircraft at airports in the US is one such example of forward planning or lack of.
- CraigJPerry 5y ago
  There’s also listen-before-talk rules for devices in certain ISM bands in the EU. Affects at least LTE, Wifi and a few other users in 5.8ghz
- usrn 5y ago
  Our band around 400Mhz has a similar limitation.
h2odragon 5y ago
> all RF spectrum belongs to the public. The FCC does not own it, I wish the FCC and more radio enthusiasts also understood that. Its amazing how many epochal inventions in radio have come to the public through getting around the FCC one way or another.
- charcircuit 5y ago
  Not just inventions in radio. Pretty much all electronics nowadays are at least unintentional radiators.

karteum 5y ago

For people interested in regulation in EU/CEPT area, unlicensed bands (ISM and SRD) are captured in ERC 70-03, where you can see the bands and associated limitations (in terms of EIRP, Duty-Cyle, and other things) https://docdb.cept.org/download/25c41779-cd6e/Rec7003e.pdf https://docdb.cept.org/download/25c41779-cd6e/Rec7003e.pdf Annex 1 is about generic SRD. The other annexes are about other bands and/or more favourable conditions for specific applications. This may seem complex and over-regulated, but there is a good reason for that : - CEPT cares that all applications get a fair chance to access the spectrum (not just "the technology which emits the strongest signal") : for example, all Wi-SUN equipments (APs, relays and end nodes) can emit up to 500 mW (with power-control) while Lora end nodes have a 25 mW transmit power. Technical studies and simulations have shown that Lora (and siblings) would not survive if wi-sun was going to be widely deployed, and this is one reason why some parts of the bands for networked SRD have a 25 mW limitation while other parts are less constrained. - those "additional opportunities" in other annexes are made based on dedicated technical studies (to check the impact on adjacent bands/services) that do a lot of assumptions with regards to potential/future densities of devices (because what matters if often the aggregated interference, not just the one from a single device)

H8crilA 5y ago

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.

nullc 5y ago

> Twitter.com still takes 10 seconds to render 140 characters of text, but it's getting that text at the better part of a gigabit per second! Assuming your phone is laying on top of the access point. :P Some of the distances for higher speeds are so short that I wonder if we need new terms for 'wireless' (there is no wire) vs 'untethered' (you're not stuck at a specific location).

drmpeg 5y ago

> There's good news: 5GHz is not an ISM band. Part of the band is ISM. 5725 to 5875 MHz. https://www.ecfr.gov/current/title-47/chapter-I/subchapter-A/part-18/subpart-C/section-18.301 https://www.ecfr.gov/current/title-47/chapter-I/subchapter-A...

usrn 5y ago
Much of 5ghz also requires DFS which can be a pain.

alhirzel 5y ago

I love this writing style, does anyone know of similar authors?

usrn 5y ago

I've always felt like carving up the digital spectrum more specifically than just giving it to different use cases (HAM, commercial, consumer etc) is harmful. Modern digital modes can transmit over each other on the same frequency and still get the message through, they're effectively self regulating.

ranger207 5y ago

> Everyone grumbles about Baofeng people, but I've had some contact with rural police and fire departments and you would be amazed at the things their "radio technician" (chief's nephew) thinks are a good idea. @jcrawfordor, what kind of bad ideas have you heard of here?

Animats 5y ago
He's talking about these: [1] They're cheap VHF FM analog handheld radios. Prices start around US$30. They can emit on the 462 MHz and 467 MHz Family Radio Service and General Mobile Radio Service bands, usable by anyone in the US and. That's fine. They can also emit in amateur radio bands, at higher power (8 watts claimed), which requires a ham license. The device controls do not make much of a distinction between the two modes. They're often used in the ham bands by non-hams, mostly preppers, hunters, militias, and people who own too much camo. This annoys radio hams. [1] https://baofengradio.us/ https://baofengradio.us/
- sbierwagen 5y ago
  GMRS is not unlicensed. A license currently costs $70, is good for ten years, and can only be used by you and your immediate family. Baofengs are not type certified for FRS or GMRS, since their transmission power is too high and the antennas are not permanently attached. It is illegal to use them on those frequencies, even if you have a ham or GMRS license, though enforcement is nonexistent.
- fortran77 5y ago
  It's not legal to use a Baofeng on GMRS and FRS because they're not "type accepted" for this purpose though there's little chance you'll get caught.
- usrn 5y ago
  They're specifically for HAMs. You should not be transmitting on FRS with those even if the software lets you do it, that's why there's no distinction: the user is expected to know what they're doing. RE: Preppers Most of the preppers I know that bother with these get their HAM license (They usually get General class actually, so they can use HF.) Maybe you live near some poorly behaved nut cases but I have yet to meet those.