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3. ...antenna dipole clearly visible

2. ...with the case off

1. Netgear USB Wi-Fi thingy

I have been reading about Cantennas and the like, home made directional hi-gain wireless antennas. I fancy making one but I don’t like the internal wi-fi card approach; the losses and complications from using long coaxial cable at these frequencies seems unnecessary to me. I searched about on eBay for a while and found a nice Netgear USB wireless adapter.

5. ...and solder on some coax cable.

4. ...cut off the antenna

USB wi-fi dongle experiments end in failure

I cut off the USB dongle’s antenna and soldered on some coax from a laptop (see the pictures) but I found I was getting better results through the coax than through the antenna on its end!

I dropped the coax bit and soldered the antenna on directly to the USB adaptor, but it kept breaking off and repeated attempts to solder it back on ended when there was nothing left to solder to! Other people seem to have managed it but I can’t, and it is not as though I am so unskilled with a soldering iron either.

You can buy one here but i have no idea if it is any good or not (note this is for the USB adaptor only, not the cantenna too).

NetGear MA101

Instead I have bought an older USB non-dongle-type wi-fi adapter from eBay, a NetGear MA101, to which I have attached a very short coax pigtail to, so I have a long USB lead and a short bit of coax which gets over the problem of a long coax being very lossy.

(Note that the MA101 does not support the 802.11 G protocol, only A and B. This should not be a problem but maybe you would like to look find more modern wifi adaptor.)

Much better design:

Back in Wales I have more time and a genuine need for this work, the house I am staying in has no internet but next-door say I can use theirs but the signal is terrible.

The one below works exceptionally well, I estimate a 12dB gain:

In this design the network adaptor (MA 101) is sealed into a plastic food container with silicone-sealant along with the coax pig-tail in order to keep the Welsh rain (and in this case snow, and ice) out.  All that protrudes from the plastic box is the actual antenna and the USB cable.

If you are interested in buying one of these please email me, I can certainly beat the price of a Super Cantenna!

Software

Netstumbler works exceptionally well for those of us stuck with windows for “war driving”, and those of us  just testing the directional gain of our antenna designs

InSSIDer is also free, and while less use when designing cantennas, it yields interesting information about your wireless network and neighbourhood.

Cantenna / waveguide design and maths:

This website seems to be one of the best, a nice simple explanation of the maths and dimensions for a 100mm can, which is what I happen to have here and is what you are likely to find in shops as large soup tins or coffee tins.

There is also a calculator for working out the dimensions for other size tins.

The Pringles Cantenna Myth:

Great site which includes lots of good info on Cantennas and the Pringles Cantenna Myth.

If you take the time to work it out, and not just read the nonsense others have written about Pringles tubes, you will find the Pringles tube is too narrow and so your cantenna would need to be impossibly long.

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