Instructables

The Making of a Beast: Part Two, The BiQuad Antenna

So now that basics are done on the WRT54G; now it is time to create the antenna I want to use.  I have a small line of site path though some trees, to the area I want to broadcast to.  So I wanted to use a Bi-quad with a parabolic reflector.  I acquired all the parts for free, out of metal dumpster, and other scrap sources.

This instrucables was going to also include some more WRT mods; however, while de-soldering the RAM chip I damage a part of the board, so I am waiting on parts.  So now there will be a Part Three :) 

This will only discuss the making of the antenna.  One could use any antenna element of choice; cantenna, dipole, or a bi-quad.  This instructable is more about getting the juices flowing, to inspire some one to create better.  And part three will be about how it all comes together.

The Prequel
 
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Step 1: The Parts.

For the constuction of a Bi-Quad, the following parts are needed:

# A small section of 3/4 (or smaller) copper pipe, about  8". 

# A piece of square, flat, copper, if using a parabolic dish the dimesions are 110x110mm, without 123x123mm is best.  Copper clad PCB board works, I chose just a sheet of copper I found.  You can use anything coductive, I use copper because the ease of workability, and low loss; however,  you can use any metal for any part of the project.

#Coax, a LMR-195 if < 5' to the transceiver, LMR-400 if > 5',  RG-58 will work if the section is short. 

That's it.

If making a parabolic dish, one will need a dish :)  Recycled one if possible.  There is a lot of science about which size dish to use for 2.4GHz.  Personally, this is about a cheap hack job, and I can get a lot more coverage with a old TV dish (direct tv style). 

Skills & Tools needed:

# Soldering skills is a must, I used a propane torch for most of this project.  A high watt soldering iron can, and has, worked.

#  Hack saw, file, tin snips, wire strippers, a crescent wrench, flashlight.

# Ingenuity; each person that tries to match this will run into their own problems, wants, desires; we are here to help; yet, a level of McGyver like skills is a plus.  I made this using no money, I could improve greatly on it If I choose.  Make it your own.

And last but not least, educate ourselves :)  I put some great links through the steps.  If you are expert or novice, it helps knowing a little.

http://www.trevormarshall.com/biquad.htm

http://en.wikipedia.org/wiki/Parabolic_antenna

http://en.wikipedia.org/wiki/Antenna_(radio)

randellc1 year ago
Good info. I had a question though. I made one of these using aluminum for the reflector and instructions here and at http://www.engadget.com/2005/11/15/how-to-build-a-wifi-biquad-dish-antenna/ .

I haven't finished soldering everything in place, I was going to test it first. Although I can connect to the router I cannot see any networks that my computer doesn't already see. How am I suppose to connect the biquad to the router?

I first used a Canyon cnp-wf514n3 connecting the leads from the biquad to one of the antenna that I removed.

Next I tried my Belkin n600 and tried to connect to one of the 2.4gHz antenna.

Am I suppose to connect to both antennas, or use a special router. Thanks.
sayton (author)  randellc4 months ago

I used only one antenna, in DD-WRT, it has the option to choose (on most routers) which antenna to TX/RX with.

redone358 months ago
you should have not painted your dish it has a reflective paint on it already an if u paint over it it weakens the signal i use to work for direct tv an i had a few people paint there dish to match there house an over time it will weather off depending on exposure
sayton (author)  redone354 months ago

Absolutely correct!! It put this project to a screaming halt. In the next part of the project I was going to wire the status lights to flash upon the dish (reason I painted it white); however, I started running into communication problems and reverted back to a old Wild Blue dish, without paint. My performance improved greatly.

jrsblb3 years ago
Also, from my research, the shielding on the coax should be soldered to the rear of the copper pipe if I am understanding this correctly. Just a couple thoughts. Great instructable though... one of the few detailed ones that do not require and "modification" to cookware :)
sayton (author)  jrsblb3 years ago
No, it would create a drastic affect on the preformance if the shieling did not follow the feed all the way to the element. For instance one like this could have some problems http://www.lincomatic.com/wireless/biquadfeed.jpg

A great resource is: http://martybugs.net/wireless/biquad/
jrsblb sayton3 years ago
Thanks for the links. Very useful.
jrsblb3 years ago
What I am not following is as follows: The "element"is grounded to itself in a way. you see how the bottom angle touches the copper pipe? I don't think this is how it should be. Not to sound like I know what I am talking about, because I am only going off of what I have seen on other biquad style antennas. If I do get a chance to make one of these I will test the difference, But I do expect there to be a difference.
sayton (author)  jrsblb3 years ago
Your correct it does in fact ground itself, creating a sharp stop in the driving voltage. This is noteable call impedence transformation, when thinking of a quad antenna, think of it like a folded dipole streched out. The short out increase the feed point impedence to balance the bi-quad to the coax. One could go far enough to find exaclty where it need to be, or even create a matching network, but that would be silly since it works darn well as designed. Thanks for your comments, good luck on the build.
rimar20004 years ago
Good instructable! I have a question (two, really), for you or maybe another reader of this comment. I have DirecTV, and the parabolic antenna it is a little one, approx. 20-25 inches. Can I enlarge it to enhance the reception? In the rainy days, when one want to see TV, it fails... I think that adding a 5 inches width of wire mesh ring around the parable, it will improve. Will there be any legal impediment?
sayton (author)  rimar20004 years ago
You want to make the dish bigger, is that the question? Do you own the equipment or leasing it? I would check for LNB drift first before taking on any modifications. I live in WA, and we have lots a rain. Only time I have signifcant signal loss with my satelite TV or Internet is when snow is covering it. I would make sure everything is aligned, grounded good, and no corrosion on any connections. Check for signal strength, and LNB drift. If all pans out, I still would not mod the dish. Socially engineer DirecTV to make a change in your favor, a better dish, or a free service call, maybe.
Thanks for the response. I live in Argentina, here the reception problems on DirecTV are regular at rainy days, even if it is not raining in the town where the antenna is. Surely this is due to the low altitude of the satellites above the horizon, something evident when observing the parables, which point to very low altitude. I suppose that since this country is a relatively marginal concession area, the company does not show much enthusiasm to improve the conditions. I have not access to the LNB, I have not technical knowledge about that things.
sayton (author)  rimar20004 years ago
If you live in Argentina why are watching TV, I would be fishing :) If were to add five inches onto the parabolic, the LNB would have to be slid farther back to capture the added signal. This would take increased modification to the dish, and tools to test signal. I would look into getting a FTA (free-to-air) setup.
Thanks for all. Do not think that in Argentina are not contaminated waterways, as in many parts of the world. To go fishing I would have to make many km, although I have the Rio de la Plata 10 Km away from my house. In TV, I look almost exclusively documentary films (NatGeo, THC, Discovery, Animal Planet, Bio and others) and news.
For Step 2 - 3, I'm thinking that if you cut the center hole radially [X or X and +(read 4 or 8 radial cuts)] instead of drilling, you might be able to carefully fold the metal outward to create a shoulder onto which you could place a screw-type hose clamp for adjustment purposes. ~/Lee
sayton (author)  Lee Wilkerson4 years ago
Great idea!! Creating the shoulders could allow for several other things to be soldered on. Soldering on a tube with set screw, in which another tube slide through could work. Thanx
wow very professional, i love the sticker to!
yeah it does look like somthing some big company would sell... sept the cat would be a DELL or somthing.. lol
Scott_Tx4 years ago
Very nice. I've got an old dss myself and was going to put a USB wifi in the focal just to see whats in the neighborhood.