
Simple Wi-Fi Yagi (2014) - cyanoacry
http://ham-radio.com/k6sti/wifiyagi.htm
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mediocrejoker
This makes the antenna more directional. It increases the range in one
direction while decreasing it in every other direction, so I'm not sure how
well this would work for most people without relocating the router/AP.

That being said, it's a clever bit of engineering.

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fovc
My current (rental) place has the router and AP in one corner of the
apartment, so signal strength at the other end is terrible. Is there a better
(cheap but effective) option than this?

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cyanoacry
You can try adding a parabolic (or circular) reflector:
[http://www.freeantennas.com/projects/template/](http://www.freeantennas.com/projects/template/)

As with the original link, the antenna is directional (and since it's a
reflector, probably even more directional), so you lose out on flexibility.
It'll be quite good if you don't plan on moving the other point, though.

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modeless
What is the legality of this? I have a vague suspicion that operating a device
like this would violate some FCC regulations.

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turbohedgehog
FCC regulations (afaik) only apply to the power output of the device,
modifying the antenna like this shouldn't change the power output.

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grahamburger
FCC regulates EIRP, which is output+antenna gain. For this to be strictly
legal you would need to adjust the power down until the EIRP is within the
legal limit. Actually to be strictly legal I think it would need to be type
excepted by the FCC.

That being said if you're using this in your home/office on a legal channel it
would be _really_ difficult to even tell from outside you were using it and
almost certainly not worth the FCCs time to even try to watch for it. It's not
_that_ much extra gain over the stock antenna.

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colanderman
To be fair, the FCC regulates both EIRP (4 W / 36 dBm) and max transmit power
(1 W / 30 dBm). E.g. you can't just have a 34 dBm transmitter hooked up to a 2
dBi dipole.

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vinhboy
So this makes the router sends a stronger signal, farther. But how does this
help if my laptop still has the same wifi adapter and can't send a strong
signal back?

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stephen_g
It also makes the antenna more sensitive in the direction its pointing. The
elements make the antenna more directional, sort of focusing the energy. This
increases the transmit side by concentrating the energy into a smaller area,
but the same effect also helps it collect more energy.

The trade-off is worse performance perpendicular to the extra elements.

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bbayer
I am wondering if antenna calculations are applicable for all types of
routers. If not, how can I adapt it to my own setup?

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bsamuels
itll be applicable for any 2.4ghz, 50 ohm radio

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fake-name
Not really. It's only really applicable to any router that uses a dipole
antenna.

Pragmatically, this means it's only really an option on routers with external
whip antennas. Lots of routers have internal antennas, at which point you're
going to have problems attaching the thing. Also, if the internal antennas
aren't dipoles, it's not an option at all without significant redesign.

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dragontamer
> dipole antenna

Erm, looks like a monopole antenna to me. The rest of your post looks correct
otherwise.

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

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jlgaddis
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](http://www.arrl.org/antennas)

[1]: [https://www.arrl.org/shop/ARRL-Antenna-Book-23rd-
Softcover-E...](https://www.arrl.org/shop/ARRL-Antenna-Book-23rd-Softcover-
Edition/?page=1)

~~~
Splendor
And/or find a local ham radio club.

[http://www.arrl.org/find-a-club](http://www.arrl.org/find-a-club)

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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.)

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geforce
Depends. Some routers have multiple antennas because there are multiple
transceivers inside it, and some technologies (i.e. MU-MIMO in 802.11AC) will
most likely react strangely having one of their antenna modified. In the end,
it would probably make your performance even worse.

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anfractuosity
Basic antenna question: I thought with Yagis the elements where connected
together, is that not the case? As they seem to be held just by plastic.

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kale
No, Yagis have a single driven element like a dipole, and you have longer
elements behind the driven element (reflectors), and shorter elements in front
(directors I think?).

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anfractuosity
Interesting, thanks!

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tumblen
Could something like this have any impact on a bluetooth antenna?

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mojoB
Certainly, though the output power is quite a bit less (20dBm for WiFi vs 4
dBm for typical bluetooth).

[http://www.tomsguide.com/us/how-to-bluesniper-
pt1,review-408...](http://www.tomsguide.com/us/how-to-bluesniper-
pt1,review-408-4.html)

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ramgorur
interestingly, the antenna optimizer (AO) software uses genetic algorithm to
find the right the antenna topology, therefore, this antenna is not designed,
it's evolved. more details can be found here:
[https://en.wikipedia.org/wiki/Evolved_antenna](https://en.wikipedia.org/wiki/Evolved_antenna)

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amgin3
I wonder what this will do for my 20DBi external wifi adapter.. I can already
connect to networks over 600 meters away from my 13th floor apartment..

