UHF Ground Plane Antenna

I needed an antenna to use in my apartment, but have limited space. I had been using a cheap mag-mount antenna on a cookie sheet, but I decided I wanted something better. Doing some research I decided on a Quarter-Wave ground plane antenna. For UHF frequencies it is small and also easy to build.


The initial calculations were done from M0UKD's website.

Vertical length = 0.162m = 6.38in

Radial Lengths = 0.181m = 7.126in

From these values I used 4NEC2 to model the antenna with 4 radials at 45 degrees and a wire diameter of 0.064in (~14AWG). Using these values the minimum SWR is 1.097 at 437MHz. The SWR is under 2 for the entire 70cm ham band.


The antenna was very simple to build. Everything was attached to a SO-239 panel mount connector. Some ~7AWG solid copper wire was used for all of the elements. The four radials had ring terminals soldered to the ends to connect to the four holes on the panel connector. The end of the vertical element had to be filed down to be able to fit in the center connector.