Directional/Sector DIY Antennas

[test_23277]

Hi,

I'd like to share some Directional/Sector DIY Antenna designs with you. More often than not, an omni-directional radiation pattern isn't what you need. Even if it actually is, you may consider 3 routers with Bi-Quads attached to them in a 120 degree orientation to each other (see: GSM base stations). If you're into DIY (I am), this is for you.

1. Bi-Quad (sector radiation pattern)
There's a lot of information on the net about this particular design. A good starting point is at http://martybugs.net/wireless/biquad/

2. Cantenna (more directional than Bi-Quad)
Same here. Good starting point is at http://www.turnpoint.net/wireless/cantennahowto.html

3. Yagi-Uda (from my experience, comparable with Bi-Quad as far as the radiation pattern is concerned)
There is a thorough tutorial available at http://www.heise.de/netze/artikel/Die-0-Euro-Antenne-223704.html (in German). Don't be fooled by this one! It's a beast if build correctly. Hint: I recommend balsa wood/super glue combo.

It's very important, that you build these very "anal retentive", i.e. very precisely - this is HF. I built all of these with awesome results, i.e. much higher coverage+throughput in Mbps.

[WorldSpot]

Hi

Thanks for sharing this also.

I have a question about this: When you setup 3 wifi AP each for 120degrees, do you use different channels and ssids?
Do you use some kind of shield between antennas to avoid interferences?
If using the same channel, when an antenna is emitting, the 2 others even if they are sectorial will receive the emission, and using multiple routers is not very useful in this case.

Even if not using the same channel, will the wifi radios be selective enough to avoid interferences?

[test_23277]

I actually haven't thought the 120 degree setup whole through yet. I never actually built such "base station" myself. I just mentioned it to point to another possible use-case for these DIY antenna designs besides point-to-point, sector utilization (that's what I use currently with just one AP).

That said, if I'd (personally) implement the 120 degree setup, I'd - spontaneously - go for non-overlapping channels 1,6,11 for the respective APs to avoid interference the best that I can. I'd think (this is speculation though, before actually doing it), that all presented Antenna designs (especially 1 and 2) have enough of a directional radiation pattern not to interfere with each other too much, especially when using distinct channels.

My current favorite for a one AP setup, is the Yagi-Uda design as it's really easy to build (precision certainly needed) and it's really worth the effort. I operate a sta/client mode router with this design and my throughput to the host AP more than doubled by just attaching the Yagi-Uda to the omni-antenna the router ships with.