HEX BEAM, Overall Description

By K4KIO (k4kio@leoshoemaker.com) – Page revision date 6/2010

By PU7IRR (rossijunior@bol.com.br) – Word edition date 12/2010

This file provides guidelines to build a G3TXQ broad band hexagonal beam R.F. antenna for the six amateur radio bands, 20, 17, 15, 12, 10 and 6 meters. This antenna is featured in the March 2009 edition of QST magazine and is a significant improvement over the Hex-Beam design.

The hexagonal beam offers a number of features as follows:

•    Gain and front/back comparable to a two element Yagi.

•    Five bands with low SWR

•    Broad band characteristics

•    Low weight and low wind load

•    Construction from general hardware components

•    Ease of adjustment

If you have been to other sites on construction of the hexagonal beam you might be a bit confused. You see, some sites tell you how to build the “original” hexagonal beam which is patterned after the design of the HEX-BEAM, a trademarked product of Traffie Technologies. The wires for this original design for a single band look from above, like an “M” over a “W”.

For a more full understanding of the technical parameters of the G3TXQ broad band hexagonal beam, visit the web site of its inventor, Steve Hunt, G3TXQ. (http://karinya.net/g3txq/hexbeam/)

If you feel you would rather not get into building your own G3TXQ broad band hexagonal beam, I can build one for you. See the Hexagonal Beam by K4KIO for sale details here. (http://k4kio.com/)

This  original  design  is a  good antenna  and owners  of the HEX-BEAM  are  quite vocal  about  its performance as were builders of the homebrew version. I used to be one of the homebrew builders and was so enthusiastic that I published a set of guidelines like these to help others build one.

But, things have progressed a little and thanks to the exhaustive work of Steve Hunt, G3TXQ, a slightly different configuration of the hexagonal beam has been discovered. Viewed from above the wires for a single bander look like the sketch to the right.

Which one is better? Well, owners of the original HEX-BEAM are very loyal. But the only competitors in the market are selling only the new broad band hexagonal beam and home brewers are all building that version of the hexagonal beam instead of the original. And here is the reason why.

This is a G3TXQ broad band hexagonal beam for 6 – 20 meters. It is just less than 22 feet in diameter and is constructed of six fiberglass tubes and 14 or 16 gauge stranded copper wire. The center post is a five foot piece of fiberglass or PVC. The beam is fed at the top of the center post with 50 ohm coax and weighs about 25 pounds.

The hexagonal beam consists of two elements for each band. The driven element is in the shape of an “M” and the reflector element is wrapped around the four spreaders to the rear of the driver wires. The elements are made of wire instead of tubes used by most Yagi antennas Therefore there is a need for a supporting structure. The supporting structure consists of six flexible fiberglass tubes attached to a base. The tubes are as shown and thus the name hexagonal beam.

The antenna elements are held in place by the base/tube structure, the wires and Kevlar/Dacron cords. All bands of the antenna are fed by a single coax cable. To the right are sketches of how the G3TXQ broad band hexagonal beam is configured for a single band. A sketch of the wires of a five band hexagonal beam can be viewed here.

The support structure for the hexagonal beam resembles an umbrella upside down. To the left, wires only for a five band hexagonal beam are shown. The wires for 20 meters are the outermost and 10 meters are the innermost. The gaps between the ends of wires are insulated end spacers which keep the tips of the driver wires and coupling. reflector wires at the specified distance from each other for proper

The driver wires are fed with a single coax from the top with each band’s driver wires connected at different vertical positions on the center post (handle of the umbrella).The spokes of the hexagonal beam are flexible tubes that keep tension on the wires while supporting their weight.

The classic hexagonal beam has been in use for several decades and a commercial version is available for purchase in a variety of configurations; multi-band, mono band, etc. Many, including the author have built home brew versions of the HEX- BEAMR and used them quite successfully. Guidelines for building one are available on other sites for those who prefer to stick with the tried and true.

The classic hexagonal beam, for its compact size, is fairly narrow banded in its front/back and SWR performance. This is one of the trade offs for the compact physical size that makes the classic hexagonal beam so attractive. In late 2007 Steve Hunt, G3TXQ conducted extensive testing and modeling   of   many   variations   of   the   classic hexagonal beam seeking to overcome its narrow banded deficiency without sacrificing the simplicity and small size. The design featured in this G3TXQ broad band hexagonal beam is the result of his efforts in this regard. A full explanation of the design is available on Steve’s web site. An overall comparison of the new broad band design and the classic design is available. These guidelines are based on my own construction of the G3TXQ broad band hexagonal beam.

The original or classic hexagonal beam is the configuration of the Hex-beam manufactured by Traffie Technologies and copied by many homebrewers. The classic hexagonal beam is a proven winner among those who have built one. However, the classic beam has a significant shortcoming that is a result of its compressed configuration. It is rather narrow banded. In fact, if you design your classic hexagonal beam for use on the SSB portion of the larger bands such as 20 or 15 meters it will perform quite well. But you will find that the front to back performance on the CW end of the band is quite mediocre if not downright unacceptable. You can adjust the wires for resonance at the middle of the band but then it will be only average in performance on both the SSB and CW sub bands.

In November 2007, Steve Hunt, G3TXQ, developed a major improvement in the classic hexagonal beam to overcome these bandwidth limitations. The new G3TXQ hexagonal beam is much broader in its performance and as a result will deliver quite good front to back performance as well as low SWR over the entire range of frequencies of the larger bands. Below are charts that illustrate the differences in the classic and broadband hexagonal beams on 20 meters. The only penalty to be paid for this improved performance is a slightly larger diameter of the broad band. The five band classic hexagonal beam for 10, 12, 15, 17, 20 meters is about 19 feet in diameter; the broadband is 22 feet.

This minor difference in size for such a major improvement in performance causes me to recommend the G3TXQ hexagonal beam over the classic. I have modeled both, I have built both, I have tested both and I have used both. And I am convinced that the G3TXQ broad band beam is better. At the urging of the late L.B. Cebik, W4RNL, Steve recently authored an article featuring the broad band hexagonal beam in the December 2007 edition of the ham radio on line antenna magazine, AntenneX.

Below is a comparison of the classic and the broad band hexagonal beams.

Top view of a five band classic hexagonal beam antenna showing wires only with no spreaders or other supporting structure. Diameter is 19 feet

Top view of a five band G3TXQ hexagonal beam antenna showing wires only with no spreaders or other supporting structure. Diameter is 22 feet

Construction of the G3TXQ broad band hexagonal beam is easier than the classic hexagonal beam:

•    No terminals for the reflector on the center post

•    Only two end spacers per band rather than four

•    Reflector, driver and spacers are a single loop making adjustment much simpler

•    Tuning is not as critical because the bandwidth is broader

Data for five band beams on 20 meters at 30 feet above good ground. Azimuthal patterns at 29 degrees elevation. SWR for 50 ohm feed.

The SWR of the G3TXQ hexagonal beam is dramatically better on the low end of the band making it easier to couple the transceiver to the antenna for maximal power transfer.

The forward gain of the G3TXQ hexagonal beam is slightly better than the classic design.

Azimuthal radiation patterns for the classic hexagonal beam and for the G3TXQ hexagonal beam. Note the slightly superior forward gain and the significantly superior front/back performance of the G3TXQ hexagonal beam.

The front/back gain ratio of the G3TXQ hexagonal beam is dramatically better than the classic design. This means that unwanted signals coming into the transceiver from the back of the beam will be much less than with the classic hex beam.

Note: the peak of front/back performance of the classic version occurs at 14.05 MHz whereas the SWR at this same frequency is about 2.2:1, a sub-optimal point on the SWR curve. What this means is that it is necessary to compromise between optimal SWR and best F/B with the classic design. On the other hand, with the broadband version, the front/back performance peaks at the lowest SWR with the result that there is no need to compromise between these two major goals in beam performance.