Basic Design:A modified 20 meter Extended Double Zep Operating Bands: 40 thru 10 meters (with tuner)
|The NB6Zep antenna is simply the easiest wire antenna to build, with high
performance for ham radio and SWL use. Only a dipole would be easier to construct and
maintain. Unlike a dipole, the NB6Zep will operate on all ham bands 40-10 meters
(including the WARC bands) with no strain on the antenna tuner, transmission line or
operator. When you follow the basic rules for this antenna and use good common sense
construction techniques to build this antenna, you will receive reliable results as shown
in the documentation I have provided here.
I live in an area with severe antenna restrictions. Not even TV antennas are found on the houses in my neighborhood! For the last eleven years I have been operating successfully on the HF ham bands by hiding my "evil activity" in the pine and fir trees that line the back yard of my home in Beaverton, Oregon. I have experimented with many designs and techniques for wire antennas over the years and have learned what works and what does not work. I have 5 wire antennas integrated into the back yard, but the single most valuable antenna I have is the NB6Zep at 40 feet above the yard! A NEC wire modeling program is needed to keep all of my wires operating properly in the space of a typical back yard. I have spent many hours using EZNEC to model the NB6Zep antenna. The total length is optimized to fit in the space of a 40 meter half wave dipole and the feed line length is optimized for good operation when attached directly to a tuner with balanced output or when used with a 4:1 balun device. I am happy to share with you the details for building your own NB6Zep.
Basic Construction: The wire must
be installed as horizontal as possible. Do not invert or "dog leg" the wire as
this will impact expected performance. The wire and feed line are light enough that it can
be mounted with just the two ends supported. A strong 18 AWG wire is used to make both
legs of the center fed antenna. Cut each leg exactly to the same length of 38 feet. (33
feet horizontal and 5 feet to hang down vertical.) Use a heavy duty ceramic or plastic
insulator for the center to connect the wire legs to the feed line. CLICK for DETAIL
The feed line length should be 49 feet long for open ladder line and 41 feet long for
TV twin lead.
Basic Performance: While waiting
for the rain to stop so that I could install the antenna at 40 feet, I operated for
several days with it stretched between two trees at 6 feet off the ground. Good psk31
contacts were made from Oregon to the East coast with 50 watts on the 40 and 30 meter
bands. (High angle radiation is very under rated on the low bands). The antenna was
brought to 40 feet, supported by two light gauge steel Radio Shack masts strapped to the
upper trunks of two pine trees about 70 feet apart. The antenna is broadside to the SE and
NW. All of the design data from EZNEC is based on the NB6Zep at 40 feet off the ground and
with no large objects or other tuned antennas in the near field. The gain of the NB6Zep is
based on the maximum field from a 1/2 wave dipole at a 1/2 wave length above ground. Your
performance will differ if, for example, you have dipoles, yagis or any horizontally tuned
antennas in the same yard as the NB6Zep. Your results may differ if your antenna height is
less 35 or greater than 45 feet. You should consider removing other horizontal antennas as
they will be mostly obsolete with the NB6Zep installed.
Construction and Performance Notes:
Ceramic "egg insulators" are hard to find these days, but I have had good
results over the years making my own wire antenna insulators from plastic coat hangers.
(Use the flexible round type purchased in stores, not the free hangers from the dry
cleaners.) They are very strong and UV resistant. Cut 3 inch sections and drill holes a
1/4 inch from the ends. Use them at other lengths for wire spacers.
The NB6Zep Story: Once upon a time, in a land far to the Northwest, there was a full sized 20 Meter Extended Double Zep antenna supported only by two majestic pine trees. The trees both stood at the very outer regions and at opposite corners in the land known as NB6Z. This span of distance allowed the EDZep to spread, although the weight of the feed line at the center could not be supported, causing a rather unsightly and disconcerting droop to be seen. Despite the odd appearance of this stately antenna, it continued to serve its' master well for many years; with many fine contacts on all bands from 40 through 10 meters. It occurred on one winter's day, that a fierce storm blew down one of the two pine trees that had supported the EDZep. This caused much anguish to the master of the land, who immediately gathered his forces to find an acceptable solution to this dilemma. Several seasons of trial and error passed, but no resolve could be made. Finally, after much calculating and re-calculating, a new design configuration was found and a new support tree was christened. Much to the delight of the master of the realm, it was found that this new design had no droop to catch ones eye. Further joy was had when the on-air performance of the new antenna was found to be just as good as the original! Overcome with joy, the master named this new design NB6Zep, after the land in which it resides. He further decreed that the new design be shared throughout all the land of Hamdom and with all who seek to enter the Kingdom of Ham.