Modify a Stock Wifi Antenna

This instructable will guide you through the process of hacking a stock 2-3db Linksys 2.54 gHz antenna into a 7db omni.

Antenna specs were taken from:
http://martybugs.net/wireless/collinear.cgi

That website is a great resource for a variety of antenna and wireless projects. I highly recommend it :)

Please take a moment to review the picture notes, as I will be referring to various parts of the antenna during the instructable.

Step 1 Materials and Tools

Materials

• 300 mm of Copper solid core wire, 2.5mm is ideal. (Most power cords have solid core wire in them. Try scavenging from there)
• Solder
• Shrink Tubing
• A 250mm length of PVC pipe (ABS would work as well). I used 1/2 inch diameter, as it is cheap and gets the job done.
• Two (2)  PVC end caps
• Epoxy glue
• A collinear antenna ( From a wireless router or WLAN card or dealextreme.com)

Tools

• Two pairs of needle nose pliers
• a hammer
• Vice-grips
• Bench Vise (optional, but so very handy)
• Soldering Iron
• Exacto-knife, or some sort of razor blade.
• Heat Gun (or a lighter)
• Wire Strippers
• a piece of metal stock or a thick screw driver to use as a template for the antenna.

Comments

[IronManMC]

Boosting the signal with amplifiers adds noise to the signal. WiFi antenna amplifiers are receive only, making your WiFi into what I call a "Reverse Alligator" (all ears, no mouth). If they can't hear you.....

Getting a stronger signal by using a high gain antenna is much better, and cheaper. If it's directional, this further improves both transmit and receive while allowing us to reduce undesired interference by aiming.

I built the "cookie can antenna", made from a Pepperidge Farn Pirouette cookie can. To increase gain, I used a 4" to 6" adaptor, into a 6" to 12" rectangular adaptor, and ball piened it into a more circular shape. I sanded off the paint, clamped it with a large hose clamp and the "straight" flange from the 4"-6" adaptor (to make a handle), and sweat soldered both unions. The gain of the single-cone version is spec'd around _18 dBi. I figure the total gain of mine is around +25 dB. I used a short pigtail to N connector, and from there, uber-rigid LMR400. This has only 6.6 dB loss per hundred feet. I have a 25 footer and 15 footer, both with male and female N connectors, so my loss figure for both cables is probably closer to 2 dB. I mount it on a 20 foot mast, and turn it by hand.

[DrakeWoodring]

the length of the whip states it should be greater then 3/4 wavelength, but the length mentioned is less the 3/4 (since 3/4 is 91.5mm and the whip is only 83)

Is the measurement correct? Or should it be longer?

Thanks!

[timbit1985]

It was an error on the sign, sorry. it should be <3/4

[Mikeya68]

COOL INSTRUCTABLE, WHAT IS THE NET GAIN IN WIFI AREA?

[timbit1985]

It really depends on what you mean by your question. If you are speaking in pure dB, then you can expect anywhere from 3-5dB gain over a stock antenna. If you are speaking in terms of physical area increased, I am not sure. The variables that affect RF broadcast are different at each location :)

[lazyNinja]

is the pvc necessary or can the wire be antenna be left naked?

[timbit1985]

The wire CAN be left naked, but it is a rather delicate affair. I would strong encourage you to protect it with pvc or some other microwave transparent material. Also, if the bare antenna touches a metal object you risk grounding it, which could fry your radio transmitter. Alternatively, you could leave the wire insulation on. If RF can get through a wall, it can get through 0.5mm of insulation.