• If you have any questions about the ON4AA Center-Loaded Off-Center-Fed Dipole (CL-OCFD) antenna, or
  • If you like to discuss OCFDs or single-wire-fed Windom antennas, or
  • If you would like to share the results of any of these antennas you have constructed,

then, please, do JOIN the Windom Antenna Join the Windom Antenna Yahoo!Group

ON4AA-200 CL-OCFD 6-Band Version

Design Goals

Like many fellow radio amateurs, I own a fairly standard shortwave radio station consisting out of a good quality HF transceiver driving a 1kW tube power amplifier.

Click to enlarge!

PA output filter-tank

I never chose to spend money on a kW-rated (balanced) antenna-tuner since the adjustable pi-network of the output filter-tank of my power amplifier allows me to tune out VSWRs of up to 3÷1. The goal that I set out was to design an HF antenna, with a VSWR of 3÷1 or less over the full bandwidth of as many amateur radio HF bands as possible, with a preference for the low- and the non-WARC bands. This design goal has been achived with a new kind of antenna;

The Center-Loaded Off-Center-Fed Dipole Antenna (CL-OCFD)

On target

In order not to tease your curiosity any further, you will find an EZNEC-calculated VSWR-graph of the antenna below. This is an antenna that works without a tuner over the entire bandwidth of the 80, 40, 30, 20, 15 and 10m-band, simply by adjusting the output-tank of your tube power amplifier. (If you have a transistor amplifier as a final stage, you definitely will need an antenna-tuner though.) In such, this antenna is the first single-wire antenna described in literature offering these capabilities.

ON4AA-200 CL-OCFD @16.75m: VSWR vs Frequency