14 dBm EIRP = 25 milliwatts, typical legal max for wifi, and the -5 dBm/MHz EIRP power spectral density says that 25 mW must be spread over an 80 MHz channel.
This is about radiated power in any direction not exceeding what you would get with an omnidirectional 1W antenna.
So beamforming under these rules lets you use less input power for the same directional power. But it doesn't let you bundle all your power into a single direction.
Yes. Beamforming for the receiver, tho, is highly beneficial. MIMO does that for you. The previous poster is correct, the EIRP must not increase when antenna gain does; you have to turn down the wick on the TX.
A microwave may generate waves with many hundreds of Watts but the FCC limits the allowed leakage to ~the same effectively radiated power as they do Wi-Fi in the 2.4 GHz band.
the only real limit is until you start interfering with other people to the point they notice and complain. it's not like the FCC has vans roving the streets looking for unlicensed TV usage like the BBC but for wifi.
They aren't sniffing around residential homes unless they have a reason to suspect someone is interfering with someone else's licensed spectrum, but if you're _selling_ a device that doesn't comply with the legal limits they will see you in court.
The FCC does hunt down illegal AM/FM broadcast transmitters in residences. They publish several forfeiture orders every month for pirate radio stations (often in residences,) whether their interfering or not. Hunting these is lucrative business given the PIRATE Act (S.1228) and its hefty fines.
I've never seen this happen for a WiFi band operator, so yeah, they're aren't looking. They certainly could though: someone is using all those grey market boosters. Some of those have enough power to show up for many miles, and triangulating them is quite easy.
They do go after cell jammers. One example from 2016 was a guy in Florida using one in his car during his daily commute. People complained their signals failed at about the same time every day and the FCC pursued it and caught him. $48K fine.
Enforcement action is likely driven by complaints from other users.
Both FM broadcast and telcos pay for their exclusive slices, so enforcement happens quicker.
That's speculation. I know what is written in the notices and orders. The orders do not cite either complaints or determinations about interference. The notices do. Some of these document complaints with the formula: "in response to complaints." Others do not, such as this[1].
My inference is that when actual complaints exist they are documented, for evidentiary reasons. Thus, when the existence of complaints is omitted, no such complaints exist.
It also depends how long your pirate station operates. If you run maybe 30 minutes in irregular intervals and don't bother anyone, no one will care too much and by the time a van comes around to triangulate, you're off the airwaves.
But if you run for hours every day, and you run a shitty PA with a too wide bandpass filter, that jams other stations? Oh boy you'll get v&.
I once loaded firmware on my Linksys WiFi router to allow me to use the Japanese channel that is illegal in the US. I thought I was so smart until I realized that nothing else I owned could use it.
One reason regulations like this exist is to save people the burden of having to worry that some asshole will suddenly start transmitting in a way that interferes with you and you’ll have to go to the trouble of complaining. You can proceed on the general assumption that other people will be acting within the agreed limits.
It’s a very selfish attitude to take to say ‘Ah, I’ll just crank up the gain til someone complains’ rather than ‘I guess I’ll stick within the guidance so I don’t inconvenience anyone’.
This site is called Hacker News. It's a place where people like to tinker, poke, prod, probe things to see what it is they can do with it. It's pretty fundamental to take something and see if you can make it go to 11. There are ramifications to some of these "hacks". Knowing that and how to avoid getting caught is part of the DNA of the hacking ethos. Sometimes, your hack is harmless. Sometimes, it is slightly annoying. Sometimes, it is flat out illegal. Knowing exactly (or trying to find out) how far you can bend without breaking is part of the culture.
Once again, I say that you can push your TX higher than "accepted" and for the most part get away with it. If you push it higher to have negative consequences on other people (especially those other hackers that feel slighted) will seek to fix the glitch.
I'm really confused on how this original comment is so lost on here.
> the only real limit is until you start interfering with other people to the point they notice and complain. it's not like the FCC has vans roving the streets looking for unlicensed TV usage like the BBC but for wifi
In the area of radio, you must be extremely careful with this mindset. Keep in mind that interference may affect important / safety-critical infrastructure (and you may not even realize). For example, I am frequency facing issues from wifi (with deactivated or nonfunctional DFS) towards a weather radar in the same band (which indeed is the primary user, and weather forecasts are critical to aeronautical and maritime safety ! This is a nightmare to troubleshoot).
If you want to tinker with radio, I would suggest to pass your HAM radio license (which will give you the minimum background with regards to radio, propagation, regulations, etc.).
Because an increasing number of people do not care anymore about any regulations, I see many administrations worldwide are increasingly pushing for locked firmwares and bootloaders (i.e. no more openwrt), more import control, etc. If you want to still be able to tinker with hardware and radio in the future, you should always ensure peaceful coexistence with others i.e. know what you are doing and work within the boundaries of regulations (be it txpower, duty-cycle, listen-before-talk, etc. Those limits are there for a good reason !).
Radio waves, air, water and DOCSIS cable modems have one thing in common: they're all shared spectrum. Whatever you do affects everyone else in the same medium - and unfortunately, there are always dumbasses who ruin the fun for everyone else.
People trying to hack their DOCSIS modems and flashing firmware from other countries disrupt everyone on the same trunk cable. People thinking they'll just beef up the PA on their crappy wifi AP to get a better signal instead of adding a second AP cause enough noise to disrupt an entire neighborhood, especially if the PA output fries (part of) the bandpass and now there's side emissions all over the place. People burning wet wood in their ovens because they can't be arsed to dry it properly or, worse, outright burning trash stink up the entire 'hood. And people taking dumps in the rivers were enough of a problem in medieval times already that warnings like "it is forbidden to crap in the river on <day> because the next day beer will be brewed" [1] were commonplace.
That radio interference was the reason FCC almost banned alternative router firmwares ten or so years ago.
The compromise that allows openwrt to exist is the radio drivers being signed binary blobs.
Folks were modifying stuff for more power, more "channels" and disabling dfs and apc. So it did not happen for no reason.
And now vendors like Ubiquiti and Mikrotik have special USA models with more locked down firmwares.
Others have already covered the legal problems with this. I’ll add that going over 1W or even less with typical WiFi gear can introduce enough distortion to offset the power gains.
WiFi hardware is cost optimized. It’s likely that the PA chips in your radio are going to distort if pushed past the legal limits. Many radios distort heavily past 100mW.
Its common for people to turn the power setting all the way up thinking they’re getting the best performance, but best performance might occur at a lower setting.
Someone trained/learned/schooled in this stuff might know that. But for a curious hacker getting at the internals of how something works, the first instinct is to turn it up. That's their learning path. It's natural curiosity. More must be better. Louder must be better.
The point is to stop scaremongering about letting people turn up the TX. It's just a damn WiFi radio. They aren't going to be blocking their neighbor from listening to their favorite ClearChannel session of commercials. At most their neighbor might get a bit of interference. But if you're running on the same channel as your neighbor, you're already asking for trouble. Nobody's going to emergency, nobody's going to jail. We're not talking about firing up an 100kW flame thrower of a radio signal here. Let's just everyone keep their knickers on and realize the context of what we're discussing
> But for a curious hacker getting at the internals of how something works, the first instinct is to turn it up. That's their learning path. It's natural curiosity. More must be better. Louder must be better.
If you increase the TXpower way beyond the P1dB of your PA, you will introduce distorsion and therefore harmonics beyond your operating band (i.e. you can end up disturbing RF services other than wi-fi, possibly safety-critical services). https://www.everythingrf.com/community/what-is-p1db
> But if you're running on the same channel as your neighbor, you're already asking for trouble.
This isn't true, WiFi handles same-channel interference better than off-channel interference. Especially newer standards have more tools to deal with it like BSS coloring.
Translated the linearity of your PA (nevermind LNA for RX) is unlikely to support even 20dBm, and the higher rate modulations for even 802.11a/g (nevermind any MIMO/SDMA workings) are EVM limited, not received power limited
It's peak-to-average power ratio (PAPR) or Crest factor [1].
It's not a really a big poblem for those who know, the limiting PA can be replaced or bypass with with more accommodating ones that can transmit higher power with better linearity and power envelope tracking.
Ha. My friend and I had the FCC van roving our neighborhood looking for us once, back in the late 70s. A guy with a CB base station dropped a dime on us, cause we were playing with our 0.1 watt walkie talkies near his house. The guy that sold us the handhelds said “what channel crystal do you want, how about 9?” and we said sure; we didn’t know that 9 is the emergency CB channel and the law prevents its use for, for example, playing hide and seek as a 13 year old.
Of all of those hypothetical "if you could go back in time" situations, I'd want to go back and rat that guy out for selling kids that crystal.
Just the other day in another thread there was the conversation about mischievous people doing things, and that pretty much sounds like what that guy was doing. He got the best of both worlds knowing he was going to cause some chaos but none of the repercussions of it.
To be fair, there are a lot of people in the FPV drone community using 600mW+ 5ghz transmitters for analog video without HAM licenses, and I don't think I've ever heard of anyone getting in trouble for it. But that's typically in unpopulated areas.
To quote that PDF as it was a bit hard to find within the many dozens of pages:
Pg. 95: Very Low Power Device. For the purpose of this subpart, a device that operates in the 5.925-6.425 GHz and 6.525-6.875 GHz bands and has an integrated antenna. These devices do not need to operate under the control of an access point.
Pg. 98: Geofenced Very Low Power Access Point. For the purpose of this subpart, an access point that operates in the 5.925–7.125 GHz band, has an integrated antenna, and uses a geofencing system to determine channel availability at its location.
Most newer band definitions specify the limits less in wattage and more in EIRP that measures the actual output of the antenna instead of just the power applied to the antenna by the transmitter. They also specify how the power as to be spread through out the channel and how sharply it has to fall off outside the channel. [0]
[0] See page 3 for an example definition of a VLP definition and requirements from earlier this year. It specifies EIRP and how the power has to be distributed so you're not throwing one big spike in the middle of the channel for example.
> The Further Notice sought comment on the appropriate power levels as well as other rules for VLP devices to ensure that the potential for causing harmful interference to incumbent operations is minimized. (6 GHz Further Notice, 35 FCC Rcd at 3940-42, paras. 236-43.)
