OK4 Radio Miskovice

Drycleaner's antenna for 430-440 MHz

Copyright © Jindra Vavruska 2003, 2005

This antenna is made of iron hangers (probably zinc-coated) on which they deliver my suite each time I pick it up from dry-cleaners. After several months of business with my favorite drycleaner's shop, I came to realize that I had a large number of hangers. Iron wire diameter is roughly 2 mm. Yagi elements are stiff, yet easy to make with common home equipment. Antenna impedance was designed to be 50 ohm in order to avoid complicated matching.

Boom is made of a plastic beam available at local DIY store. Feel free to use wood or anything else, as long as it is electrically non-conductive and low-loss on UHF.

Driven element is a folded dipole. I took some length of the wire, approximately 2.5 time the calculated length of the driven element. I found its center and made marks 1/2 DE length less some overhead for bending (take 1/2 the bend diameter as estimation). I bent one end, then measured again from the edge to the other side and bent the other end so that the total distance edge-to-edge was the original calculated driven element length, or at least very close to it. Then I adjusted the middle gap by pliers to make it approximately 1 - 1.5 times the thickness of the coaxial cable (in my case it was RG-58 -- yes, please don't lough too loud). I made coaxial balun of RG-58 and soldered it to the folded dipole.

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Dimensions
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Modelled impedance plot
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Modeled radiation pattern at 430 MHz
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Modeled radiation pattern at 435 MHz