In February, 2006, I built a prototype antenna for Amateur Radio Direction Finding on the 80 meter band. The antenna is a shortened vertical, supported by a 20' telescoping fiberglass pole. The vertical is 5.5 meters tall, with a 55 cm tall loading coil of 170 turns at the top of the bottom section of the pole. It has two radials, each 5 meters long. As it happens, no matching network was needed, as the antenna came out with 1:1 SWR at 3.5795 MHz. It was designed with the help of the LOADCOIL software program by Reg Edwards G4FGQ.
This is not, by any means, the best design for an 80 meter vertical antenna for most purposes. The software claims it will be 10 dB down from a full size quarter wave vertical. It does, however meet the requirements for a good ARDF antenna - compact, portable, and self-supporting.
These photos are copyright © 2006 Kenneth E. Harker. All rights reserved.
|The antenna is being supported by a fishing pole holder that is designed to be stuck into the ground/sand. The vertical and the radials attach to the plastic box with phono plugs. On the underside of the box is a BNC antenna jack.|
|This photo gives you an idea of how large the coil is. The coil is held in place at the top and bottom with electrical tape. In a real production version, I'll probably wrap the entire length of the coil with Scotch 33+.|
|Looking up the telescoping fiberglass pole. The 12 guage stranded wire is periodically attached to the pole with electrical tape.|
|The box is attached to pole with cable ties.|
Last Updated 14 April 2016