17 ms·
Good intuitions. FCC regulations restrict EIRP[0], which is essentially "what is the signal strength in the strongest direction". It's possible that increasin
by aray 10y ago
Good intuitions. FCC regulations restrict EIRP[0], which is essentially "what is the signal strength in the strongest direction". It's possible that increasing directionality of your antenna puts you over the EIRP limit (given how routers already try to get _really_ close to it to improve performance).
[0] https://en.wikipedia.org/wiki/Equivalent_isotropically_radiated_power https://en.wikipedia.org/wiki/Equivalent_isotropically_radia...
- colanderman 10y agoYep. Specifically you'd need to adjust your TX power down to 27 dBm (from a max of 30 dBm) for an AP, or 29 dBm for a station. http://www.air802.com/fcc-rules-and-regulations.html http://www.air802.com/fcc-rules-and-regulations.html gives a nice summary. Basically APs on 2.4 GHz are only allowed 36 dBm (4 W) EIRP, no matter what antenna shape. This is usually not a problem though, since stations tend to have weaker transmitters anyway, but will still benefit from the AP's enhanced antenna gain.
- Spare_account 10y agoOK, so if by the time the signal exits my property it has dropped below mandated limits, there is no harm done right? If I aim my antenna such that I contain the illegal power region within my property, will there be an unintended consequence? To be clear, I'm referring to a house not an apartment so I don't have any concerns about upstairs or downstairs neighbours.
- ocdtrekkie 10y agoI think FCC laws technically apply within your property as well. Hypothetically, what happens if your non-compliant device blocks a visitor on your property from calling 911?
- sjwright 10y agoI think this falls under the pragmatic category of "you're only breaking the law if you get caught."
- ocdtrekkie 10y agoOh of course, and there's actually a surprising number of FCC rules you'll never get caught breaking. GMRS license violation is another.
- hydrogen18 10y agoNo, that is incorrect. The domain of the FCC extends to all property of the United States of America, be it public or private.
- colanderman 10y agoThe reason this is important is that it prevents private corporations from interfering with public air space (as discussed previously on HN [1]), and prevents landlords from interfering with the rights of tenants to legally place outdoor antennas (such as satellite dishes). [1] https://news.ycombinator.com/item?id=8406022 https://news.ycombinator.com/item?id=8406022
- colanderman 10y agoRF energy doesn't quite work like this. If your transmitter has a high EIRP (either due to antenna directionality or high TX power), then its signal is going to travel a long way, even after the signal level has dropped to that of a lower-EIRP transmitter. That is simply the inverse square law at work. You could place sufficiently absorptive materials that this isn't so (e.g. enclose your house in a Faraday cage). But as hydrogen18 points out you're still limited by the FCC.
- tropo 10y agoHe's not operating under FCC part 15. He's using FCC part 97 instead, with the appropriate license. His rules: 1500 watts PEP, unlimited EIRP, channels 1 to 6 only, no encryption That's better than a normal microwave oven.
- tlrobinson 10y agoNote that licensed ham radio operators are allowed to operate at (much) higher power on the WiFi channels that happen to overlap the 13cm ham band. http://w5vwp.com/wifihams.shtml http://w5vwp.com/wifihams.shtml (Of course then you are subject to all the Part 97 restrictions like no encryption, no commercial use, etc)