Untitled Document

Wire mesh parabolic reflector dish

Concept:

For boosting range of wifi and mobile communications.
Can be used with wifi, 3G, radio.
Scrap / low cost materials.

Essentially a big satellite dish.
Mesh with holes smaller than a certain size will reflect microwave and radio waves like a solid surface, and is much cheaper, lighter, less affected by wind, and easier to work with.

Prototype:

(Click images for larger, opens in new tab)

One of the first problems I had to solve staying in the valley in New Zealand was how to get internet into the place. This dish worked beautifully. We didn't even bother aiming or optimizing it, just chucked it out, pointed at a tree, with a 3G dongle kind of in there somewhere, peaked out at over 100 kilobytes per second. Nearest cell phone tower was I think about twelve kilometres away, down a rather bushy river valley.

Tutorial:

First, mark out the templates on plywood. You'll need 4 of the red one, 4 of the blue one, and 2 of the green. This is if you want to make the 1.5 square meter dish, you'll need to scale the numbers for different sizes.

To draw the parabolas the easiest way is to get yourself some light chain. When a chain hangs it makes a catenery curve, which is reasonably close to a parabola.
1. Mark off a length of chain as described on the template (135 cm for the blue, 160 for green).
2. Attach that length to the ply at the points marked, making sure they are the right distance apart.
3. Spraypaint over the chain to mark it's curve.

Cut out the templates with a jigsaw or similar.

Slot them all together, like so:

The easiest way to firmly attach everything is just drill some holes in appropriate places and cable tie it all together.

Then attach your chicken mesh. If you're using this to receive 3G mobile/internet signal you'll want to have the mesh size no larger than 40 mm diameter. We figured that out using wikipedia and maths.

1. Drill 4 or 5 holes in the ply per gap, near the edge where the mesh will be attached.
2. Get yourself about 200 cable ties.
3. Cut off a rectangle of mesh to cover half the dish.
4. Press the mesh into the cradle so that the point halfway along one side sits right in the middle.
5. Attach this point with a cable tie.
6. Work your way out in an expanding circle, pressing the mesh into the cradle and attaching with ties until the whole thing is locked down, including the circle perimeter. Don't worry about getting this perfect, it's not a mirror, and is pretty forgiving.
7. Repeat for the other half of the dish, overlaps are fine, but you can trim them off if you like.

Now attach two lengths of string tight from the sides of the circle, so you know where your centre is, and can attach your dongle/antenna/mobile there.

You're done!

Chuck it somewhere appropriate.

You can download the 3d model and schematics here:
Rhino3D 3dm file 203 KB
Google Sketchup 3DS file 39 KB

Results / Field Data / Maintenance:

Works good. Still need to test it for range, but other than the 12km 3G range, also managed to connect with usable signal to a home wifi router from about 4km away with line of site and a 1 watt usb wireless adapter.

I suspect it would do better still with a cantenna or biquad antenna on the receiver.

Email: solarflower.org@gmail.com Facebook : facebook.com/groups/solarflower.org/