Building the dirtiest UHF antenna

A project log for Waffle: a pocket-sized digital radio system

┬ÁController, CC1101 module and LCD forming a small communication device. Other probable uses in the near future.

M.daSilvaM.daSilva 05/09/2016 at 15:170 Comments

I'm still waiting for the boards to come in... In the meantime, I built an UHF antenna I could use for a base station that could withstand 20-50W.

The design is based on a plain old quarter-wave (0,164m in lenght) ground plane antenna, like this one from M0MTJ:

                              1/4 Wave Ground Plane AntennaI used brass for the radiating element and the radials. They're a bit sturdier than copper, though I don't know how it affects performance.... It can't be worse than those stainless steel whips! The antenna was brought to a 1:1 SWR match using an antenna analyser, by trimming the antenna with a pair of pliers.

The support is made of 3D printed PLA, as an effort to try and have as little as possible parasitic metal elements in the vincinity of the antenna. I still have to find nylon bolts and screws to lessen that impact even more.

The PLA part is attached to a nylon rod which has been milled to ensure a nice mating surface. This rod is also non-metallic as to ensure as little parasitic effects as possible.

The nylon rod will then be mounted to the actual mast, which I don't have yet.

The last part, the tripod, was built using scrap metal parts from around the shop. The three legs are held to the central body with three butterfly nuts and lock washers. A piece of pipe was welded on the top of the structure.