Modifying old dish network dish for wifi

Hi, I am new here. I am trying to modify an old dish network dish to get better wifi reception. I gutted the reciever part of the dish, hogged it out and made room for my USB Wireless Dongle. Will this work? Will it be any better than a tin can? Do I need to paint or cover the dish with aluminum foil? Here are some pics, Thanks Greg

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gregbr549 hath wroth:

Nice idea, but I don't think it will work very well. Where to start....

No need for aluminium foil cover. There's plenty of wire mesh under the fiberglass. Or, if it's a metal dish, it will reflect 2.4GHz as well as the original 12-13GHz.

The big problem is that you don't have a feed that is matched to the dish. In transmit, the USB dongle radiates in all directions. Most of it will get reflected to who knows where by the metal horn. My guess is about 1/10th of the radiated RF actually hits the dish and goes in the desired direction. In receive, it's not so bad. The USB dongle probably gets all the RF that is reflected from the dish. However, that means you'll have more gain in receive than in transmit.

To see how this works, scan through this article on feed design.

The next problem is lack of gain. The maximum gain of a dish antenna can be calculated. Assuming you did everything perfectly, and the feed was properly matched to the dish f/D ratio, then: Maximum gain for a 0.6meter diameter dish: gain = 9.87 * Dia^2 / wavelength^2 * (feed efficiency) gain = 9.87 * 600mm^2 / 125mm^2 * 0.4 gain = 91 dBi = 10 log(91) = 19.5dBi The 40% efficiency (that's the 0.4) is probably optimistic. Again, that's if everything is lossless, perfectly matched, built correctly, and properly designed. I don't think your feed qualifies.

Let's say that the USB dongle works as I described, where only 10% of the RF gets to the dish in transmit. 1/10th is: 10 * log(0.1) = -10dB loss So your final gain will be about: 19.5dBi -10dB = 9.5dB gain. That's not much more than a much smaller and easier to build biquad or coffee can antenna. That's also why you want to spend some time designing a proper matched feed.

I don't really agree with these, but they might be of interest.

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