Simple Wi-Fi Yagi (2014)

[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.

[colanderman]

Given that it's only somewhat directional, this would actually be useful for the common case that the AP sits in a corner of a one-story house. No sense sending all that RF energy outside, so direct it inside.

[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?

[bjackman]

This would be great if you lived on a boat, then you could have a wifi router on the shore/marina with signal directed at your boat.

[modeless]

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

[aray]

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...

[swiley]

You're not allowed to mix and match antennas on mass produced Part15 devices, regardless of the ERP. That never seems to stop anyone though.

[agumonkey]

I remember reading that unless you amplify the radio above 5W or something, there's no way you're above the regulated limit.

[turbohedgehog]

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

[diminoten]

Right? Why wouldn't the router companies include this somehow in their designs if it actually improved performance?

Because it's illegal, is why.

[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?

[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.

[microcolonel]

Reciprocity says that path loss is equivalent both ways.

[anotheryou]

I'd guess it goes both ways, just like a speaker cone and the cone of an ear.

[dragontamer]

Antennas are coupled. Transmitting is receiving, and receiving is transmitting.

When you pull on a chain or a rope, it doesn't matter if the other side is "receiving" the pull, or "sending" it. The two sides are physically coupled.

Similarly, antennas are physically coupled to each other. Increase the gain on one side, the other side still benefits. You're physically connecting a "rope" of electrons over the air.

[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?

[bsamuels]

itll be applicable for any 2.4ghz, 50 ohm radio

[MayeulC]

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

[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

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

[Cerium]

Take a microwave design class. This would be a second or third course after electrostatic, electrodynamics, then something like microwave theory. At my school we had to petition for the course as a special section. It was great, we built cavity resonators, and final project was an antenna design. All the way from theory, then using modern fea antenna software, and then building it and testing performance. If you have any interest take it. I was not going to but the professor said: "Phil, what's the lower end of the microwave spectrum?", I said "1 GHz", he then asked "How fast is your computer?", I replied "2.8 GHz", He said "I'll see you next semester then?". these days having an understanding of microwave theory will help you no matter your specialization.

[kogepathic]

1. Find a university course on RF, look up the course textbooks.

In my university we had several courses on "analog electronics" which covered topics like free space path loss and RF concepts (e.g. bandpass filters).

2. Use Google or another search engine (DDG) to find the book in PDF or EPUB version.

3. Enjoy reading the book without forking over hundreds of dollars to a greedy publisher.

[crwu]

balanis

[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.)

[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.

[bsamuels]

theres a two reasons your router probably has 3 antennas:

-beamforming

-split 2.4ghz/5ghz/5ghz-wave2 antennas

if your router is using those three antennas for beamforming, you might trigger some strange behavior if you yagi a single one of them. if run into issues and can turn beamforming off, you should be able to yagi a single one no problem.

if your router pumps each antenna into a separate radio, then you can reliably pump a single radio into that corner of your house w/ a yagi. however, you won't have seamless roaming between the 2.4ghz and 5ghz networks when you move into and out of that corner of your home.

i recommend getting a mesh network, they're the bees knees and are a huge step above the traditional access point + range extenders model

[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.

[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?).

[tumblen]

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

[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...

[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

[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..