The NB6Zep HF Antenna

Basic Design: A modified 20 meter Extended Double Zep Operating Bands: 40 thru 10 meters (with tuner) Dimensions: 66 feet horizontal, 5 feet vertical Transmission Line: Open Ladder or TV Twin Lead Materials: Conventional low-cost wire antenna construction

The NB6Zep antenna is a simple wire antenna that's easy 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. Use a medium duty ceramic or plastic insulator at both ends of the horizontal wire to serve as a tie off point for the antenna support and to support a 90 degree bend to drop the last five feet down vertically. CLICK for DETAIL Attach a medium size lead fishing weight at the end of the wire to keep gravity working for you. Use a section of nylon twine (string) to hold back the vertical wire from wrapping itself around the support mast or other objects when the wind blows. CLICK for DETAIL Mount the NB6Zep as high as you can manage to support it. Drop the feed line down or away from the antenna at 90 degrees for as far as possible. Keep the feed line away from metal objects if possible. The line may be attached directly to a tuner with balanced output. CLICK for DETAIL If that is not possible, construct (or purchase) a 4:1 voltage balun to add a short run of 50 ohm coax back to the tuner. Make a short loop in the line where the balun is attached to keep rain out of the transformer. CLICK for DETAIL 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 than 35 or greater than 45 feet. You should consider removing other horizontal antennas as they will be mostly obsolete with the NB6Zep installed. 40 and 30 meters: The NB6Zep performs like a half wave dipole, with broad, medium to high angle lobes running off the sides of the antenna. Very good for regional and for long distance skip. The antenna displays very little directivity on the low bands and is performing very well in all directions. 20 meters: On this important DX band, the NB6Zep has it's highest gain, over 3 dB. There is a sharp medium angle lobe running 90 degrees from both sides of the antenna. CLICK for DETAIL For the first few contacts on 20 meters with the NB6Zep, I reached Texas, Utah, Alaska, Korea, Japan and Argentina, all with strong reports. A good QRP contact to Japan was made on PSKHELL mode. CLICK for DETAIL The antenna produces very sharp lobes from each side, good for long distance and regional skip. 17 and 15 meters: On these bands the NB6Zep produces two broad lobes spaced 45 degrees from both sides of the antenna; each lobe has gain. This looks like a butterfly pattern when viewed from above the antenna. CLICK for DETAIL The antenna performs very well for long distance with it's low angle radiation and also has medium angle radiation for shorter skip operation. 12 and 10 meters: On these higher bands the NB6Zep produces two narrow lobes with gain, seperated by 60-80 degrees from each other on both sides of the antenna in an "X" configuration. CLICK for DETAIL Two layers radiate from the antenna giving very good operation for long skip and shorter skip conditions. As on 20 meters, the NB6Zep is very directional on 10 meters. NOTE: An 80 meter option is described HERE 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. Always solder every wire connection and then insulate connections from water seepage. Also insulate around all exposed coax braid. Use "hot melt" glue or a silicon rubber sealant like RTV. CLICK HERE to see some of the basic materials and tools I use to construct wire antennas. You can make your own light weight balun using Iron Powder Toroid cores. The smaller T130 HF material (red) cores work fine for several hundred watts. Follow the diagrams in the ARRL handbooks. Use a hand drill to twist 20 AWG enameled wire into winding sections used in bi-filar and tri-filar transformers. Make about 12 turns onto the core for good performance. Wrap layers of electrical tape around the balun to protect the core from damage. (Cores are like glass and once they are cracked they are not usable.) Use medium weight nylon twine for all of your wire antenna construction and support needs. It is extremely strong and lasts forever. If possible, align your NB6Zep in the direction that places lobes where they will reach the largest population of ham operators. Nulls in the antenna above 30 meters can be useful to reduce local noise sources that are picked up by the mostly horizontal polarity of the NB6Zep. A diagram showing the current distribution on the NB6Zep antenna system for the major bands is FOUND HERE The NB6Zep should perform well at lower heights, even down to 20 feet. The take off angle will be effected by becoming lower at heights above 40 feet and higher for lower construction. It is possible to have good operation with the legs inverted down from the center feed point, however, the diagrams provided here are not valid unless the antenna is horizontal with the ground and in a straight line. The NB6Zep is not a "tuned" antenna and will not interact significantly with other antennas in the yard. You could construct several NB6Zeps to have selectable directivity for the bands above 30 meters. 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 (NB6Z). 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.

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