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Comment by radisb | Hacker News Reader

Hypothetical question: I buy some land to host conventions. I make the buildings and enclose them in a big faraday cage. Then I make deals with anyone that agrees: Whoever wants to host a convention in my center, they will accept that inside the convention center, there will not be any kind of transmission, except my own wifi. Leaving aside the ways I could accomplish this, is what I want legal?

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There's a hack you could do to make it so it is illegal for people to operate Wifi in your convention center.

Wifi spectrum is shared with other services. I am aware of at least the following services that use all or part of the same spectrum that 2.4 GHz wifi uses:

1. Radiolocation services (e.g., radar).

2. Industrial, Scientific, and Medical (ISM) devices operating under Part 18 of the FCC regulations.

3. Amateur radio (ham) operators operating under Part 97 of the FCC regulations.

4. Wifi, RF remote controls, Bluetooth, microwave ovens, cordless phones, wireless microphones, and many other things, operating under Part 15 of the FCC regulations. (Note: note all instances of all of these devices will be in the 2.4 GHz band. For instance. There are other bands available for most of these, and which a particular device uses is up to the manufacturer).

There may be other services operating under other parts of the FCC rules that I did not list (because I don't know about them).

The above are listed in order of priority. The rules are simple:

• You cannot interfere with users of services above yours the list. For instance, if a ham radio operator interferes with an ISM user, the ham has to stop the interference. How he does that is up to the ham...he could reduce power, or use a directional antenna aimed away from the ISM device, or move to a different frequency, but if he can't stop the interference by such means, then he has to stop transmitting.

• If a user of a service above you on the list interferes with you, it's entirely your problem, not theirs. They have no obligation whatsoever to take any steps to reduce or eliminate their interference with you.

So here is the hack. Get some part 18 certified ISM device that is very sensitive to interference from wifi--so sensitive that it is pretty much impossible to operate wifi near it without interfering--and operate it on site. Now anyone who fires up wifi will interfere, and you can ask them to stop and if they do not they are violating FCC regulations.

I think you have #2 and #3 backward. ISM is unlicensed and can't cause interferences to ANY licensed radio services, that's including amateur radio users.

I checked the regs, and looks like they may be effectively on the same level.

47 CFR 97.301 says that the sharing requirements for hams in 2.390-2.450 GHz are given by 97.303(d), (e), and (p).

97.303(e) says: "Amateur stations receiving in the 33 cm band, the 2400-2450 MHz segment, the 5.725-5.875 GHz segment, the 1.2 cm band, the 2.5 mm band, or the 244-246 GHz segment must accept interference from industrial, scientific, and medical (ISM) equipment".

So, hams must accept interference from ISM in that band, which would put hams equal or below ISM on my list...BUT I cannot find anything that says hams must not interfere with ISM, which would indicate hams should be equal or above ISM.

The one thing about ISM is that a lot of those are actually transmitting only; for instance, microwave oven. The fact that amateur radio service needs accept interference from ISM equipments just indicates the fact that hams can't report instances of interferences to FCC (as long as such devices are operating under proper conditions as described under Part 18) and unlicensed services usually receive very little protection, if at all, from interferences caused by licensed services.

Blocking wifi is illegal absent security issues:

https://www.fcc.gov/document/warning-wi-fi-blocking-prohibit...

It doesn't matter if you own the land. Land ownership does not confer rights to the airwaves, the air space, and often things like mineral rights.

Not sure. If someone has a cell phone and needs to call 911, would you be held liable for their inability to make that call?

I dont know, but it's my property and it seems logical that as long as they know they cant make that call, the decision is theirs and so is the liability.

> If someone has a cell phone and needs to call 911, would you be held liable for their inability to make that call?

I've been in plenty of buildings with terrible-to-nonexistent cell reception. I somehow doubt that they'd be held liable if I wasn't able to get reception to make a 911 call. I can't see that the large Faraday cage example is appreciably different.

The FCC begs to differ: https://www.fcc.gov/document/warning-wi-fi-blocking-prohibit...

So it is illegal. So basically I am not free to block hot spots in my own area if I use it for public access, which essentially amounts to "Even if you own an area, whenever it is publicly accessible, you do not own its 'air'". I find it a bit too restrictive.

A lot of people want land ownership to mean that they have absolute dictatorial power over everyone and everything on their land. We, as a society, have decided that this is silly, and that most crimes outside your land remain crimes inside your land. I can't really disagree.

No it doesn't. That ruling is about the illegality of deploying a wi-fi protocol that's meant to interfere with other communication.

A purely passive barrier to electronic signals is a completely different thing. There are no rules against Faraday cages, and the FCC is perfectly aware of them and what they are for; it OKs the use of Faraday cages for use with experimental radio technology that would otherwise require a special permit.

I've always worked on the assumption that it is within my right to build my private facility out of copper if I choose, and the fact that your cell phone doesn't work in my facility is your problem not mine. I am not "jamming" any signals. I would be interested to hear counter-arguments from those familiar with the FCC rules on this matter.

Maybe if intent to jam wireless could be demonstrated, but there are no codes I know of that require a certain level of permittivity in a building, and indeed many buildings all but squash signals- and that is the user's problem.

I've always wanted to open a bar where cell phone and wifi signals are blocked.

I'd put big signs up announcing that fact, and it would be awesome to see the kinds of people that actively want to hangout where cell phones don't work.

I mean the retro bars in Chicago ban cells. I am sure the west coast has some too.

You could do that. Just ask people who you see using cell phones and laptops to leave. You don't have to resort to violating federal law.

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