Quados antenna

We, dear anonym, reviewed the design of a Wi-Fi antenna proposed by the Serbian radio amateur Dragoslav Dobričić (YU1AW) called the Amos antenna. In 2008, he proposed a new, rather interesting design of a loop antenna (BiQuad) with many elements, which he, by analogy with the successful previous design, gave the name Quados.

The idea of this design was born on the basis of the study of the BiQuad multi-element antenna. Each doubling of the squares number should result in a 3 dB increase in the antenna gain. However, calculations and practical tests show that this is not the case. The increase is much less and the making of such an antenna is, to put it mildly, unjustified. What is the reason?

The reason is that the individual squares are located "end-to-end" to each other. This leads to overlapping of the separate square aperture by the apertures of the neighboring squares. The aperture of the dish antenna is always less than its real area. For wire antennas, the aperture looks like an "aura" surrounding the wire, and in this case the aperture extends beyond the square. To solve the problem, Dragoslav Dobričić proposed to slide apart the squares from each other and connect them in an antenna array using λ/4 segments of a two-wire balanced transmission line (a similar one can be seen on the Bowtie TV antenna). The design is calculated and optimized by the 4NEC2 program. According to calculations, the gain of the 6-loop Quados antenna is 3 dB higher than that of the 6-element BiQuad antenna, which flickers in the header banner of our site and reaches 16 dBi. It must be understood that an increase in the antenna gain is attended by a narrowing of the major lobe of the radiation pattern and the antenna becomes sectoral. In this case, the radiation pattern narrows in a plane perpendicular to the antenna axis. As you can see in the figure, the radiation pattern of the Quados antenna is similar to that of the Amos antenna. This is clear. We have essentially the same design, where the straight elementary dipoles are replaced by loop ones, and the transmission lines between the emitters are modified for this case. The fundamental difference here is that the antenna receives a horizontally polarized wave, unlike the Amos antenna. If you rotate it by 90°, it can be used in 3G-4G networks. However, setting it in the direction of the base station will require more patience.

The input impedance of the antenna is about 200 ohms, and for balancing and matching with a 50-ohm feeder, the author used a half-wave loop from an RG58A coaxial cable, just like for the Amos antenna. The emitter is attached to the reflector with polyethylene poles cut from the coaxial cable inner insulation. Here is what the finished design of the Quados antenna from four squares looks like:The site has an online calculator for calculating the Quados antenna with which you can recalculate the antenna to other frequencies. The number of squares can be increased. The main thing is that there should be an even number of them and symmetry with respect to the connection point should be maintained. Estimated antenna gain:

• 4xQuados - 14.7 dBi
• 6xQuados - 16.5 dBi
• 8xQuados - 17.6 dBi

For weather protection, the author suggests covering the connection point with silicone sealant, and placing the entire antenna in a plastic box.

Links with detailed photos of designs:

• Author's article - YU1AW;