Quarter-Wave Ground Plane Antenna

I followed calculations and instructions to build a quarter-wave ground plane antenna from some wire and a UHF connector that I picked up at the last Ham Fest in Harrisburg. I cut everything a little long and soldered it together. I trimmed the radials to about 54-inches and folded and rolled the radiator wire to a length that is resonant at 147MHz. I measured with the NanoVNA. Once it was at the right frequency, I found that bending the radials up and down could adjust the SWR at its lowest point on the graph. Keeping the radials slightly flatter had a lower SWR than the 45 degrees suggested in the original design.

This ground plane antenna feeds from the bottom, which is physically more sound than the vertical dipole I had up previously. I tested it last night when I strung it up, and it reaches Harrisburg and Parkesburg with no problem.

antenna  2m 

See also