This is a biQuad, and a double-biQuad antenna. You can find the construction guide (in Fr) here. As usuall the photos is in the Brest-Wireless gallery. The small one is about 11/12db. And the biggest one: ~ 14db!! May 23, 2014 - To study and understand the construction of a simple double biquad antenna. Android application “WiFi SNR”. Wi-Fi router. You need some theory to answer this - it's not entirely simple. Consider that each quad loop really consists of 2 dipoles, with the ends connected together (at the corners of the quad). So, each quad loop really acts as two dipoles located parallel to each other. (The reflected loop, in a similar way, consists of two of these 'pseudo-dipoles'). So, if you then consider what would happen if you would extend the dipole to double its length: Instead of one dipole (which has low impedance at its center), you'd have two dipoles, which have a very high impedance at the center - almost impossible to feed (thousands of Ohms). But it would still be possible. Cracked version of solidworks free variables. What's not so interesting is that a large part of the field irradiated by the dipoles would cancel each other (because they're too close), so you would probably 'feel' a slight improvement, but not nearly what you'd expect from such an effort. Edit: Modified the text slightly to - hopefully - make it less confusing thanks for the remark, Phil). Making use of the edit, do note that if you'd extend the sides to 3/4$ lambda$ you'd actually get 3 dipoles and low impedance. But again, the gain won't be what you'd expect, as, again, parts will cancel. Moreover, if you'd think about using the biquad as a feed for a parabola, you'd be covering a much larger part of the useful area. ![]() Lo and behold, the humble yet mighty biquad. The gain figure on one of these things is pretty impressive, you're looking at 8-10 dBi. The double biquad detailed a bit lower is about 2-3 dBi higher. A quad biquad (an octquad?) would be around 1 dBi higher still. Construction Construction is very simple. I used a bolt, sanded so as to be solderable on a beer can taped to a cardboard backing, as seen here: The wire is enameled copper transformer wire; For a double or a quad, this is necessary, but any old wire can be used for a single biquad. The red sheet is electricians' insulating tape, used to ensure insulation between the feed points. Dimensions are pretty exact: Tolerance is about 5% and bandwidth about 10%, though it's ~25% to unity gain. Each square edge is an exact quarter wave of the centre frequency you're interested in. This is about 31mm for the 2.4GHz 802.11b/g band. The coax feed connects, in these images, above and below. A common mistake is to connect side by side, resulting in a folded dipole which has piss-poor performance. The reflector, ideally, is infinite in size. In the real world, however, the radiation pattern does not extend more than about a quarter wave around the antenna's sides. Build too big rather than too small for the reflector plate. Also ensure a good connection between the plate and coaxial ground/braid. The distance between the antenna elements and the plate must be as near as damn it lambda/8 (half a quarter wave), this causes constructive interference between the direct and reflected waveforms and adds about 80% to the forward gain of the antenna.
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