NOT Coax cable !
It is suggested a 450 – 600 ohm line.
This antenna also requires the use of a matching network “Transmatch” at the transmitter end of the feed line.
WH2T used a 75 meter band Double Extended Zepp Antenna with very good success. He affirmed to have worked all 50 states and several countries with 100 Watts using theantenna on the 75 meter band.
With a good antenna tuner the antenna will work 6 thru 160 meters, but this antenna will only tune the 160 meter band if the open wire feed line is the proper length.
More info on Double Zepp Antennas
The Zepp, short for Zeppelin is any resonant antenna end-fed by ladder line.
A Double Zepp is a center-fed 1/2 wavelength antenna.
The double extended Zepp is a dipole type Antenna consisting of two collinear 0.64 wave length elements fed in phase.
This double extended version provides 3 db gain over a dipole on the band it is designed for and each side or leg is about 5/8 wavelength long.
When measuring the wire it is very important to get each of the two sides as close to the same length as possible.
The formula to determine the length of each side is
599/Freq in Mhz = .64 wavelength.
So to design an antenna for 3.85 Mhz take 599 divided by 3.85 = 155.585 Feet per side or 155′ 7″ each side.
This 75 Meter antenna would be about 311′ 2″ overall length.
With this antenna the feed line should be routed away from the antenna at a right angle for as great a distance as possible. This will prevent current imbalance in the feed line caused by RF pickup from the antenna. A right-angle departure of 1/4 wavelength or greater is suggested.
To avoid problems matching any center fed antenna with high impedance open wire lines, keep the feedline around these lengths.
[The WORST POSSIBLE line lengths are shown in brackets]
160 meter antenna 35-60, 170-195 or 210-235 feet
[Avoid 130, 260 ft]
80 meter antenna 34-40, 90-102 or 160-172 feet
[Avoid 66, 135, 190 ft]
40 meter antenna 42-52, 73-83, 112-123 or 145-155 feet
[Avoid 32, 64, 96, 128 ft]
Some slight trimming or adding of feedline may be necessary to accommodate the higher frequency bands.
Copyright to W2HT
This article was originally available at bloomington.in.us/~wh2t/zepp.html