[HN Gopher] Unlicensed Radio
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Unlicensed Radio
Author : zdw
Score : 52 points
Date : 2022-04-14 19:10 UTC (3 days ago)
(HTM) web link (computer.rip)
(TXT) w3m dump (computer.rip)
| karteum wrote:
| 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
|
| 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)
| nullc wrote:
| > 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).
| ranger207 wrote:
| > 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 wrote:
| 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/
| sbierwagen wrote:
| 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.
| jcrawfordor wrote:
| In my experience it used to be common for rural PDs and FDs to
| just have every frequency someone could think of, within band,
| programmed into their radios regardless of authorization. I've
| even seen a rural PD distribute amateur radios to unlicensed
| officers as part of very half-thought-out emcomm plan.
|
| This is getting less common these days as more and more rural
| public safety organizations transition to state-run trunking
| networks.
| akira2501 wrote:
| > 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.
| GekkePrutser wrote:
| 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 wrote:
| 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 wrote:
| 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 wrote:
| 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
| jcrawfordor wrote:
| 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.
| h2odragon wrote:
| > 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.
| drmpeg wrote:
| > 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...
| H8crilA wrote:
| Is 2.4GHz truly unlicensed? Could I emit 500W or more with
| whatever modulation or lack thereof and not be prosecuted?
| nullc wrote:
| > 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 wrote:
| 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.
| NovemberWhiskey wrote:
| 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 wrote:
| 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
|
| 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 wrote:
| 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 wrote:
| 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.
| jcrawfordor wrote:
| 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.
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