I recently discovered that one of my roommates had attempted to boost the WiFi signal by cutting up a soda can and placing it near the router, like this:

Airport router with carved up soda can

My roommate was probably following an internet guide like this one, which advises shaping the modified can "like a radar dish" and placing it around the external antenna of the router. However, our router has no external antenna.

Will either configuration actually boost the router's reception? I don't know too much about antennae, but I suspect that the second configuration works more like a shield.

  • 3
    Have you tried measuring the result? – joojaa Jun 28 '15 at 5:46
  • Not sure what the best way is to measure it, but the network diagnostics tool on my mac gives me an RSSI of about -45 normally, and -50 when the can is placed. (Noise stays the same at -95.) So, it seems the signal is dampened. – hangar Jun 28 '15 at 16:20
  • You mean that the signal is damped. – Air Jun 29 '15 at 17:01
up vote 9 down vote accepted

What you show is a crude reflector. Yes, you can use reflectors around a antenna to get more power in a particular direction at the expense of other directions. This can be useful when the other antenna is in a known direction.

However, there are several problems with this:

  1. It may violate the law. You don't give your location (remember that filling in your profile isn't really for you, it's a courtesy for us), but here in the US the FCC will take a dim view of you exceeding allowed radiated signal strength in any direction, whether the strength in other directions is lower or not. In reality, you are unlikely to get caught, especially if the signal is weak by the time it leaves your property. This is not something you should do in an apartment building, for example.

  2. The reflector may have the opposite effect. Imagine a reflector ¼ wavelength from the antenna. The signal from the antenna, bouncing off the reflector, and back to the antenna will be ½ wavelength out of phase with the signal leaving directly from the antenna in the opposite direction. These two waves will cancel, reducing signal strength in the desired direction.

  3. At small reflector sizes, you won't get much reflection and more refraction instead. The wavelength of 2.4 GHz is about 125 mm or 5 inches. You need a reflector several times that to get good reflective effect.

  4. The shape you show makes little sense for what appears to be your intent, which is more signal strength to the right. Disregarding the small size of the reflector, phase issues, etc, the curvature is way too much help focus a beam to the right. To do that, you want a parabaloid shape with the antenna at the focus. Your reflector may be somewhat parabolic, but with that curvature the focus point will be close to the left corner of the white box.

Don't believe every hairbrain idea you see on the internet.

  • I think the (naive) intent was to boost the signal in all directions, especially the left. I believe my roommate was attempting to follow a guide such as the one I linked. Would that have been more effective? (I doubt I'll be attempting it in either case.) – hangar Jun 28 '15 at 16:23
  • @Hang: You can't boost signals in all directions this way. As for the link, I don't know since I didn't follow it and don't intend to. If it's important to the question, the information should be in the question directly. – Olin Lathrop Jun 28 '15 at 17:56

This might work to boost the signal in one direction, but it will reduce it in other directions. Antennas are often built with elements (like your drink can) that couple to the primary radiator. These act as "Directors" or "Reflectors". You see directors on a classic TV antenna - All the cross beams along the main beam of the antenna. You see reflectors on Cell Phone towers, where a tall corner sits behind the radiator to direct the signal in small angle. These both act to increase the signal strength in a particular direction. This is at the expense of signal strength in other directions. A correctly placed can like in your picture could act as a reflector, increasing signal strength in the direction it faces, at the expense of signal strength in other directions. Whether this works depends critically on the size of the reflector, and the position of the reflector relative to the primary antenna. Bear in mind this is much more likely to just reduce the signal by interacting with the antenna impedance, and reducing the quality of the match between the radio and the antenna. Like the comment above says - Experimenting will tell you which one you have.

All of these cans are made up of Aluminum. Aluminum is a good conductive material and a dense material. More dense material means more capability of conductance. They can be used as antennas to transmit the signals but I am not sure whether this thing improves the WiFi signal strength as I had not tested it by myself.

But one thing that makes sense to me is as it is made up of aluminum. It can be used to catch the signal and send it though and it is inexpensive as you see. It is just an extra layer that just increases the range a little. But you cannot say its a good replacement to those boosters available in the market.

I had not done much research about it but I can say this with my common sense.

It is too small a surface area to be an effective microwave reflector. The shape is wrong too, it must be parabolic with respect to the transmitting fractal antenna of the router. Yours is perpendicular to it.
http://www.instructables.com/id/Easy-to-Build-WIFI-24GHz-Yagi-Antenna/

With the advent of embedded fractal antennas, we no longer need external antennas sized according to the wavelength of the carrier frequency. A good development or we would have to be carrying around antennas for our cell phones. I'm not saying you can't shape an aluminum can to enhance directional transmission and reception. It just takes some design and calculation.

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