Making your own Bi-Quad (Wi-Fi) antenna

The Bi-Quad antenna is one of the handiest, cheapest and easiest to build WiFi antennas.

This blog entry will explain how to easily build one like in the picture below using cheap materials and a TNC-RP (reverse polarity tiny-N) low cost Wi-Fi router connector.

Bi-Quad antenna with Wi-Fi router connector.

Bi-Quad antenna with Wi-Fi router connector.

The antenna in the above image was designed using Antenna Magus for the following design objectives:

  • Center Frequency: 2.45 GHz.
  • Gain: 10.5 dBi
  • Bandwidth: 20% (500 MHz)
  • Feed: Coaxial feed with TNC-RP connector (typically used in Wi-Fi routers.)

Here is a diagram of the antenna with physical parameters:

Top view of the Bi-Quad antenna. Click for a 1:1 scale view.

Top view of the Bi-Quad antenna. Click for a 1:1 scale view.

Front view of the Bi-Quad. Click for a 1:1 scale view.

Front view of the Bi-Quad. Click for a 1:1 scale view.

(Note that if you click on the above diagrams they will open as 1:1 scaled versions. I decided to make them available if you want to manufacture this antenna yourself. The easiest is to print them to 100% of the original size and use these as footprints/templates to construct the antenna.)

Manufacturing process explained in 6 steps:

Step1: Cut 2 pieces of 2 mm copper brazing wire and bend to follow the profile of the printed diagram. Solder the two pieces of copper wire to form the Bi-quad?s radiating structure as illustrated in the image below.

Step 2: Bend and solder copper wire.

Step 1: Bend and solder copper wire.

Step 2: Measure and cut the ground plane to the same size as shown on the printed footprint and drill a 6mm hole in the center – I used a piece of off-cut metal that I got from a local canned fruit factory for my ground plane.

Step 2: Measure and cut the ground plane.

Step 2: Measure and cut the ground plane.

Step 3: Cut a copper spacer with a length of 30.6mm and inner diameter of > 5.5 mm. This is only to support the Bi-quad copper wire and feed. The most important requirement is that the coaxial cable needs to fit through the middle – varying the thickness by a couple of millimetres should not greatly affect the antenna?s performance. I used a copper pipe with 7.8mm outer diameter and 5.7mm inner diameter which I got from a refrigerator repair shop for R 30/meter (<5 US$/meter).

Step 3: Cut copper pipe.

Step 3: Cut copper pipe.

By now you should have the following components:

Bi-Quad components

Bi-Quad components

Step 4: Solder the copper pipe to the ground plane. Note that both pieces should be sanded to have rough surfaces and preheated in order for the solder to take easily. This can be quite tricky as the copper is a good heat conductor and cools down very quickly. (We used two soldering irons ? one standing upright through the middle of the ground plane with the piece of copper on top over the solder point. This ensured constant heat to both objects and the other solder was used on the outside to apply the soldering agent.) Here is the result:

Step 4: Solder copper pipe onto the ground plane.

Step 4: Solder copper pipe onto the ground plane.

Step 5: Solder the coaxial cable?s braid to the top of the copper pipe. The easiest is to fold it slightly over and to solder it to the outside of the copper pipe as shown in the following images.

Step 4: Solder copper pipe onto ground.

Step 5: Solder coax outer conductor to the copper pipe.

Step 6 (final step): The final step is to connect the copper wire to the feed section. The following image shows the complete antenna with the male TNC-RP (reverse polarity tiny-N) connector. These connectors are very popular and used with wireless Wi-Fi routers. They are easy to obtain and cost only a few dollars.

Bi-Quad antenna with Wi-Fi router connector.

Bi-Quad antenna with Wi-Fi router connector.

Bi-Quad antenna connected to a Wi-Fi router.

Bi-Quad antenna connected to a Wi-Fi router.

Measurement vs simulation

The following graph shows the measured |S11| compared with the simulation.

S11 Measurement vs Simulation

S11 Measurement vs Simulation

The measurement shows that the antenna is well matched over the desired band (- 20 dBi) but has an unwanted ripple on the S11 measurement. I only realised the cable and connector that I got from an old Wi-Fi antenna (also designed for 50 ohm) actually uses a 75 ohm cable which caused unwanted reflections between the connector and the radiating copper wire. I ordered a new cable and will update the post as soon as I replaced the old with the new cable.

I hope this blog entry will be useful for those of you wanting to improve your Wi-Fi reception at home!

Author: Robert Kellerman

14 Responses to “Making your own Bi-Quad (Wi-Fi) antenna”

  1. ka says:

    Hello: Many people use h=18 mm. why 30mm for biquad antennas?

  2. yusuf says:

    sir
    i have some confution that provider provided adsl(not in use now) is it work as router?N i saw so many biquad antena but nobody is telling in pc which software require to chek signal n wifi.plz provide me full theary
    so plz clarify coz i m new in this n i m learning fully with on internet.
    my id yusmusuf@yahoo.com
    plz reply in advance i m very thankful to u.

  3. the best soldering iron are those using non-filament heaters, the tip should be made of steel alloy too,’*

  4. fikry says:

    sir, how about DOUBLE BIQUAD? it’s be able to simulate and calculate the perform in antenna magus?

  5. admin says:

    We have not added the double biquad to the collection of antennas in the database, but I agree this might be a good one to add in a future release.

  6. fikry says:

    yeah sir. i hope it will be exist in antenna magus v.4

  7. KT says:

    I’m wondering how did you simulation this antenna in the software ? and what software do you use ?

  8. haryantogajahputihperkasa says:

    this high quality,wifi antena,thankyou

  9. sikandar says:

    dear sir, i have wifi linksys wmp54g v4.1 pc i card. can i use biquad antenna out door for internet access. thanx

  10. tom says:

    all your dimensions are abolutely wrong, is it in purpose or just you don't have idea about? I dont know..

  11. Admin says:

    Hi Tom, Thank you for the feedback. Just to clarify, all dimensions in this blog are in mm. I hope this will help.

  12. J Naprstek says:

    Just to note that as the antenna is not fed symmetrically (one end is grounded while the other isn't) and thus the vector of highest EIRP is not perpendicular to the reflector surface.

    I just don't remember, what is the deviation angle, but worth remembering that.

  13. nick horrex says:

    the space between dipole and reflector is 30 mm whereas elsewhere it is 15. Is this 30mm correct?

  14. Admin says:

    Hi Nick.
    Thank you for your feedback. The spacing used in this blog was 30mm. Where did you see a spacing of 15mm?

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