In order to get internet on the lab PC we needed to create a better antenna for the WiFi USB receiver. For the antenna we chose the use a biquad because it’s easy to build, provides about 11dBi gain and has a fairly wide beam width making it is to use.

The parts needed for construction

• 123x123mm square section of blank PCB
• 50mm length of 12mm copper pipe
• short length of CNT-400 or LMR-400 low loss coax (~300mm long)
• 250mm of 2.5mm2 copper wire (approx 1.5mm diameter)

• Cut a square piece of 123x123mm PCB (or any other conductive material).
• Cut the 50mm of copper in the following fashion and properly sand it to ensure a good connection.

• Drill a hole in center of the PCB and make exactly 12mm.
• Insert the pipe in the hole with the notch end on the copper side of the PCB. Make sure it’s protruding exactly 16mm.
• Solder the pipe to the pcb. You need quite a bit heat for this, so you can best use something like a heat gun.

The element is made from a single piece of copper wire, bent into the appropriate shape.

Make sure that the length of each “side” should be as close to 30.5mm as possible (measured from the centre of the copper wire to the centre of the copper wire), which is a quarter of a wavelength at 2.4GHz

Solder the element to the pipe. Solder the center of the element on to the coax cable and the ends of the element to the outside of the pipe.

Solder the other end of the coax cable to an N-connector a solder it (just like me) directly onto the USB stick

Here are some pictures of the finished antenna.