Hardware Analysis - Anyonw know how to make a Wifi antenna?

Re: Anyonw know how to make a Wifi antenna?

john albrich — 2008-04-27T20:59:00-05:00

Actually, Europe tends to be even more strict on RF output devices...

But, for an omni-directional antenna, one might try a J-pole. It's cheap and dirt simple.

http://www.marktwain.net/~aschmitz/antennas/jpolecalc.html
http://www.hamuniverse.com/jpole.html
http://en.wikipedia.org/wiki/J-pole

I've actually made j-pole antennae for various frequencies out of TV twin-lead cable. All one has to do is cut a notch in the appropriate place and trim leads to appropriate lengths. Feed using an appropriate cable to the transmitter and it's all set.

I haven't tried scaling past 1GHz, but I don't see any reason why it wouldn't scale to the WiFi frequencies.

One can also build a dirt-cheap 1/4 wavelength ground-plane antenna out of a few pieces of solid copper wire. Would take about 20 minutes.
http://www.vias.org/wirelessnetw/wndw_06_05b_02.html

A really interesting home-brew design is for a co-linear array. A well done article on this variable gain antenna can be found at: http://www.nodomainname.co.uk/Omnicolinear/2-4collinear.htm
One decides on what gain is desired, and builds it accordingly. If I were a beginner, I would start with the very simplest, fewest element 3.5dB design first, verify I can get it to work, and then only if I need to, make a 6 or 9 dB version.

For any project at Wi-Fi frequencies, lengths of the cut pieces will be quite critical and careful measurements a must.

One will also have to obtain appropriate impedance-matched low-loss coaxial feedline and connectors between the computers and the antennas. Use a "choke" (ferrite ring) as close to the feedpoint of the antenna to reduce parasitic RF along the feedline, and RF noise injection back into the computer electronics.

If one wants a directional antenna, one will have to look into things like cantenna and parabolic designs.

The issue isn't material. Certain electrical and radio-frequency requirements must be met. Just changing something from copper to slumninium or something like that won't do squat.

Making an antenna longer can actually DECREASE performance.

The other alternative as suggested above, is to find a way to increase the programmed power output of the transmitters.

edit to add-
Again, the best thing to do is research antenna design books and online resources. There's a lot of info already written on tested antenna design, some of it specifically targeted to the higher frequencies.

edit to add-
Info on simple omni-directional co-linear array antenna and this info: Examples, just search on the keywords [wifi antenna designs] and a lot of info turns up. Steer clear of the projects that look like crap or make completely outrageous claims. Articles written by an Amateur Radio Operator and include a call-sign (e.g. "X7ABC" or similar) are usually more reliable, but not always.

Re: Anyonw know how to make a Wifi antenna?

McFly — 2008-04-27T20:46:56-05:00

Changing the freq is usually a good first move.

The problem with increasing the Tx power is that ... it doesn't increase the receiving sensitivity.

Think of it this way: Two people, Computer and Router, are trying to yell to eachother across a canyon. Neither can hear the other. So Mr. Router pulls a megaphone (a Tx power increase) out of his butt and now Mr. Computer can hear him! But ... Router still can't hear Computer! Unless Computer gets his own megaphone (Tx power increase, which isn't easy or always even possible, esspically in Windows), or Router gets a bionic ear (a higher gain antenna), they're still not going to be able to communicate.

Now if this is a router-to-router setup (WDS, routed client, etc), you should be able to just boost the Tx power on both and be done with it ... although too high and you'll get massive signal degradation.

Re: Anyonw know how to make a Wifi antenna?

BoT — 2008-04-27T20:20:11-05:00

i don't know if enhanceing the antenna is a fix it all, i acyually doubt it.
what you can try to do is to look in the routers configuration and see if you can increase the power output for the wireless link and maybe switch to a higher frequency band.
it will increase your range a bit but not drastic.
i would recommand a repeater but that of course not free or even cheap.

Re: Anyonw know how to make a Wifi antenna?

GtoX (capt Guns) — 2008-04-27T19:58:24-05:00

well i dont think i have to worry about laws and regulations, europe is pretty easy on matters such as this, as a matter of fact i dont think anyone really cares over here

i just need a link or help with knowing what materials i should use, i just want to increase the strength of the wireless connection in this villa, so i can sit in any corner of the house..
any particular material that works good??

Re: Anyonw know how to make a Wifi antenna?

McFly — 2008-04-27T18:54:27-05:00

You know, I made one of those DIY parabolic directional antennas, mine didn't work for s**t lol ...

I went and bought these for my WRT54GL:
http://www.newegg.com/Product/Product.aspx?Item=N82E16833124155
http://www.newegg.com/Product/Product.aspx?Item=N82E16833999202

I didn't pay that much for them though! I bought both used for a grand total of about $20.

Re: Anyonw know how to make a Wifi antenna?

BoT — 2008-04-27T18:44:18-05:00

check this out
http://revision3.com/systm/surfer/

Re: Anyonw know how to make a Wifi antenna?

Bobby — 2008-04-27T16:49:56-05:00

So what you're saying is he should go ahead and do it?

Re: Anyonw know how to make a Wifi antenna?

john albrich — 2008-04-27T15:56:23-05:00

GtoX (capt Guns) said:

...would it work to wrap a piece of aluminum/copper string around the antenna itself and pull the wire a few meters so its kinda like a car radio antenna?

Highly unlikely. It operates at much higher frequencies and is much more sensitive to variations in impedance, length, etc.

You can read just about any Ham Radio book on antenna design for ideas.

However, you should also know that (in the U.S.) it is technically illegal (for anyone not appropriately licensed) to build or even modify an antenna for a transmitting device such as a WiFi transmitter. Penalties include fines and equipment confiscation.

If a neighbor(s) complains because of interference with something (like a portable land-line phone), it's remotely possible it could be investigated. Unfortunately (or is it fortunately) the frequencies used are shared by literally thousands of other commerical products and it would probably be hard to convince someone in FCC enforcement to investigate such a likely minor complaint.

Anyonw know how to make a Wifi antenna?

GtoX (capt Guns) — 2008-04-27T15:04:36-05:00

Hey guys i need help in how to make a wifi Wireless antenna for my Dlink router to further increase the range of it for my Girlfriends house, and its 3 stories and preferrably needs coverage throughout the whole house, as the 3rd and 1st floor have poor connection quality...

would it work to wrap a piece of aluminum/copper string around the antenna itself and pull the wire a few meters so its kinda like a car radio antenna?