Dish with USB Feed - Page 2
Monday, 07 September 2009 23:04
antanna-location1 antanna-location2Step 4.
Assemble by securing the USB WiFi adapter and cable in the dish with twist-ties, tape or glue. You want the adapter's antenna at the focal point of the dish. The adapter's antenna is typically towards the end of the USB stick (see images).

How to find the Focal Point of a Parabolic Reflector


The focal point is a point above the centre of the dish found using this formula:

f = D2/16d

Where f is Focal length, d is the depth of the dish and D is the Diameter of the dish (See the image on the right).

Note: The diameter used for an oval or square shaped 'dish' should be the dish's diameter at its widest point. Don't include the dish's lip when measuring (ie. just the reflective surface).

Enter your values in the form below to calculate focal length:
= D (diameter)
= d (depth at centre)

The focal point can also be found using a more practical method. Cover the dish with foil and point it at the sun. Place your finger at the centre of the dish and move it out till you find the hottest (brightest) point. This is your focal point.

You may need a short stick to support the adapter off the surface of the dish into this position. Alternative support methods use string tied across the face of the dish like a spider web, hollowed out plastic garden hose fittings or even chop sticks!

wifimastStep 5.
Plug the WiFi adapter into your computer with the USB cable, and set it as your WiFi card using the network settings.
Step 6.
Aim your dish at the remote WiFi antenna you want to communicate with. Your WiFi is now quite directional, so getting the aim right is important. Normally pointing the dish towards the remote antenna is best, but sometimes stray reflections from buildings etc may give good signals from unexpected directions.
usbwlanStep 7.
Once you are connected, tune your dish by adjusting its position while watching the signal meter on your computer.