The W3EDP antenna has been available for very many years: the first description of it appeared in the ARRL publication QST March 1936 in the Experimenter section under the title «An Unorthodox Antenna». It was written by Yardley Beers, W3AWH about the experiments that his friend H J Seigel W3EDP had undertaken.
The W3EDP antenna is a development of the early Zeppelin or Zepp antennas that were used before the Second World War. They obtained their name from the fact that end-fed wires were required for use on Zeppelin airships.
The antenna is fed via coaxial cable and passes through a tuned 4:1 matching transformer. It was stated in the original QST that a low value of capacitance in the antenna circuit gave by far the best efficiency.
Today, the W3EDP antenna is still widely used – it is ideal where a straightforward end-fed wire is needed for HF multiband ham radio operation. As the understanding of antenna operation was as well understood in 1936 as it is now with software like EZNEC, etc, the W3EDP antenna was designed by trial and error.
W3EDP took a long length of wire, tabulating results and progressively cutting lengths off until the best performance was obtained. A similar process was undertaken for the counterpoise. The antenna is designed for the ham radio from 80 to 10 metres bands.
Details for the W3EDP antenna are quite straightforward, and it is basically another version of an end-fed wire antenna.
The radiating elements consist of 20.4 metres and this is fed against 5.2 metres of a 300 Ohm ribbon cable counterpoise.
The W3EDP antenna is particularly useful when the station is in a room above ground. Other antennas like a simple end-fed wire often called a long wire antenna would need a good earth connection for the antenna to operate correctly. The counterpoise for this antenna enables it to operate effectively without the need for a good ground connected via a short lead.
When using this antenna, it is most likely that an antenna tuner close to the transmitter will be needed to ensure that the level of SWR seen by the transmitter is sufficiently low, otherwise, the PA protection circuits may see a high SWR and reduce the output power.
|Obviously, the performance depends greatly upon aspects such as the height of the antenna, the location, etc, but overall the users of the W3EDP antenna have confirmed that it operates well, and it is particularly well suited for portable operation because it is very easy to quickly erect.
This so-called the «New Version of the W3EDP Antenna» has an unsymmetrical wireman-feed «Zepp» and a balun 1:4. At the end of the twin lead-feeder a feed point impedance in the range of 200 – 500 Ohm with some complex part +/-j X Ohm. The Balun 1:4 gives impedances, which can be matched by the built-in ATUs of the most transceivers. The antenna has been tested from 6 m to 80 m with a coax length of 12 m. The losses are negligible and the antenna is working quite well in the praxis. If you have matching problems you can change the length of the coax cable and try it again.