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Simple Wi-Fi Yagi (2014)

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Re: Simple Wi-Fi Yagi (2014)

#31

Post by jrockway »

Yaggo wrote: post #15
diminoten wrote: post #12

Earlier quoted context omitted.

Right? Why wouldn't the router companies include this somehow in their designs if it actually improved performance? Because it's illegal, is why.

It's not illegal per se, if you adjust transmission power accordingly. Router manufacturers generally don't use yagi because it's directional, requiring aiming, unlike omnidirectional dipole antenna. Modern wifi stations have much more sophisticated ways to increase range than passive antenna designs.

Dipoles are directional too. There are nulls directly aligned with the antenna (above and below the router in this case).

No doubt this accounts for some of the "my WiFi doesn't work upstairs" stories.

Re: Simple Wi-Fi Yagi (2014)

#32

Post by diminoten »

colanderman wrote: post #19
diminoten wrote: post #12

Earlier quoted context omitted.

Right? Why wouldn't the router companies include this somehow in their designs if it actually improved performance? Because it's illegal, is why.

No, because no-one wants a home AP that only works if it's pointed at you. You can buy directional APs if you want, but they're usually used for outdoor point-to-point links, or as sector antennas. e.g. I just installed one of these today: https://routerboard.com/RBSXTG-2HnD in a place that needed a signal far from where the AP was. Usually patch antennas (like this product) are preferred over Yagis for microwave lin…

It is illegal, according to another comment:

https://news.ycombinator.com/item?id=13459834

Re: Simple Wi-Fi Yagi (2014)

#33

Post by pkolaczk »

colanderman wrote: post #19
diminoten wrote: post #12

Earlier quoted context omitted.

Right? Why wouldn't the router companies include this somehow in their designs if it actually improved performance? Because it's illegal, is why.

No, because no-one wants a home AP that only works if it's pointed at you. You can buy directional APs if you want, but they're usually used for outdoor point-to-point links, or as sector antennas. e.g. I just installed one of these today: https://routerboard.com/RBSXTG-2HnD in a place that needed a signal far from where the AP was. Usually patch antennas (like this product) are preferred over Yagis for microwave lin…

Antenna gain is a function of directionality and vice versa. Patch antennas are also good because they have often very low "backward gain" but at the same time they are not very directional forward, so they are good to be placed in a corner of a room or near a wall.

Re: Simple Wi-Fi Yagi (2014)

#35

Post by Spare_account »

colanderman wrote: post #11
aray wrote: post #9

Earlier quoted context omitted.

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_radia...

Yep. 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 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 A…

OK, 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.

Re: Simple Wi-Fi Yagi (2014)

#37

Post by ocdtrekkie »

Spare_account wrote: post #35
colanderman wrote: post #11

Earlier quoted context omitted.

Yep. 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 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 A…

OK, 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.

I 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?

Re: Simple Wi-Fi Yagi (2014)

#38

Post by baq »

if my router has 3 antennas, is there any point to installing it only on one of them? my intuition that's based on exactly no RF experience whatsoever tells me that it'll do more harm than good. (case is weak 5GHz signal in the corner of a house.)

Re: Simple Wi-Fi Yagi (2014)

#39

Post by jlgaddis »

MayeulC wrote: post #29

As an electronics student, are there any resources I could use to learn the basics of RF (antennas, etc)?

You might start at the ARRL's Antennas page [0] and consider the ARRL Antenna Book [1]. Most of that is aimed at amateur radio in particular but the theory is the same.

There's tons of free and/or open-source software (of varying quality) for modeling antennas and such as well.

[0]: http://www.arrl.org/antennas

[1]: https://www.arrl.org/shop/ARRL-Antenna-Book-23rd-Softcover-E...

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