The zeppelin antenna (or simply “zepp”) is a popular end-fed wire antenna for shortwave bands and has lots of simularities with the J-pole antenna. It consists of a long wire (half wave length), connected to one of the wires of a balanced feedline (quarter wave length). The idea is that the end of the wire has a high impedance, and the quarter wave transmission line transforms this to a low impedance, at least low enough to get to 50 ohms using a balanced tuner. A Double Zepp is a normal zepp, but the other (unconnected) wire of the feeder is also connected to a second wire. The Extended Double Zepp (EDZ, sometimes also known as Double Extended Zepp or DEZ) is the same, but the wires are now 5/8 wavelength instead of 1/2. The tricky part of this antenna is now the length of the feeder. Paul N8ITF gives you the measures for all versions of the EDZ.
So let’s imagine an EDZ for 40m. The dipole has two legs of 5/8 wavelength, so about 25 meters tall. So the 2 legs together make a total length of 50 meters, so you need a more serious garden to place it. An EDZ for 80m will be even 100 meters. But… why build such a tall antenna is you have already 50 meters of wire up in the air? So we need to modify the 40m EDZ to use it on 80m. A couple of years ago Cecil W5DXP was thinking exactly the same. So he did calculations, simulations and experiments on this idea and succeeded. Ok, he lost coverage for the higher bands (although it also works on 17m). So he now has an EDZ for 80m with only half the size of a real 80m EDZ. Hence the Half Extended Double Zepp (HEDZ) was born!
For the yearly PACC contest Adrian PA0RDA and I where experimenting (well, we were more strugling hi) with a 2x 50m wire dipole for 80m to get it suitable for 160m too. Cecil’s article really helped us in getting the right measures. So after two years we finally transformed our 80m EDZ into a 80/160m HEDZ.
I use this antenna mainly during the PACC contest and our yearly fielddays. So it has to be easy to setup. I use a 15 meter pole to put up the center of the HEDZ, and 9 meter poles at the ends of its legs.
- Dipole: 2 legs, each 48.7 meters of wire (we used 1.5mm2 / #15 AWG PVC shielded copper wire, normally used for electricity purposes).
- Feeder: 55 meters of balanced wire, made of the same #15 copper wire, and separated by rose clips.
Besides poles, wire dipole and feeder you need stuff to keep the poles erected and some rope and insulators to keep the antenna isolated from the metal poles.