A Cheap ($) 5.8 GHz Archery Target Antenna


A short backfire, or "archery target" antenna is much larger than a single wavelength for the frequency at which it is designed. It is high gain with low backlobes but the aperture efficiency is not great. My (cheap) implementation uses thin aluminum flashing/sheet cut with metal shears and joined with aluminum brazing rods by means of a propane torch. The coaxial cable of the fat dipole feed can't handle such high temperatures. Instead it's conventionally soldered on top of a a square section of single sided copper PCB which itself is brazed on to the aluminum.

The coaxial cable on the left arm of the dipole is the actual feed. It's inner conductor reaches over to the right arm. The coaxial cable on the right feeds nothing. It's a 1/4 wave balun made out of the outer conductor of the coaxial cable.

The aluminum is suspended with saran wrap and scotch tape.

My implementation is based off of S53MV's article on the Greek Microwave Group's site, "Weatherproof UHF & microwave cavity antennas". The article is also on the S53MV's own website in slightly different format.

I designed this antenna for the top of the band, 5.8 GHz before I realized my own, and most, situations required a good match down near 5.7 GHz. Regardless it's worked perfectly for point to point indoor use in low signal situations. It's a bit too directional for FPV but it does work for that too when worn fashionably taped to a hat.

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