Simple Beam to Build
Down through the years a few simple beam antennas have emerged from the pack to stay around and are used by those interested in keeping the operating costs down. These simple beams are inexpensive to construct and are usually a mono-band antenna, with the exception of the W8JK array, which can cover from 14 to 30 MHz. These beams can be constructed from inexpensive components and, if careful choice of materials is exercised, will last a long time.
Excellent DX Antennas
Most of them are bi-directional, because in the days of BR, (Before Rotors) the problem of moving your antenna was a little difficult. This would enable a ham in the central US to aim one of these antennas at Europe and be able to cover parts of the Far East at the same time. The angle of radiation is low, making them excellent DX antennas. Most of them were fed with open wire feedlines, which is rather scarce now. However, with an antenna coupler and a balun, one of these antennas could be fed with coax or 300 ohm feedline and matched with a coupler to match the transmitter properly.
Lightweight and easily rotated by a light duty TV rotator, a 10 meter version would enable a Novice to chase DX without attracting a lot of attention from the neighbors. Construction is simple, and should not pose a great problem for anyone. Wire elements taped or glued to weatherproofed 8-foot 1-1/2″ wooden dowels will work very well and are inexpensive. The old timers used to get bamboo poles from carpet shops and varnish them to make antenna elements, after the wire was taped or fastened somehow to the poles. Imagination and innovation should be used in the construction of these simple antennas.
One of the Best
One of the best of these antennas is the W8JK two-element phased array. It is capable of covering from 14 to 30 MHz completely, with no traps, coils or any other band changing tricks. CAD polar plots of the pattern show no great change in pattern shape, but the antenna impedance changes a lot during this large frequency excursion. The input impedance, at the lowest usable frequency, is on the order of 16 ohms at the lowest frequency of use, and some type of matching system is needed to set things right for the transmitter.
Matching stubs have been used with success, but that complicates the construction somewhat. An easier method to this is to use high grade 300 ohm feedline and an inexpensive coupler. Belden and some of the other feedline manufacturers used to make some transmitting grade feedline. This should be used if it can be found. Getting the feedline into the shack can be a problem, but if the tubular feed-throughs available from Radio Shack and other manufacturers are used, there should be no problem getting through walls or windows. The method used depends on your particular situation.
The JK ARRAY consists of two 1/2 wave dipoles spaced 1/8 of a wavelength, and fed 180 degrees out of phase. The phase shift is accomplished by twisting by 180 degrees the feedline connecting the two dipoles. As the frequency increases from 20 meters to 10 meters, the spacing increases from 1/8 to 1/4 wavelength, but the phasing between the two dipoles remains constant. The 20 meter half wave elements turn into two center fed full wave dipoles which will contribute some more gain to the array.
On the lowest frequency of use, this beam has about 3 dB gain and about 60 degree beamwidth. The gain figures for the higher bands have not been determined, but should be slightly higher on 10 meters because of the 1.8 dB gain available from a full wave center fed dipole. Since this antenna is bidirectional with a figure 8 shaped pattern, an interesting trick can be done with this simple beam.
Around the World
Most of our modern solid state rigs can run full break in CW, with switching times from TX to RX in milliseconds, almost microseconds in some cases. So, by transmitting a dit and listening, you could hear your own signal coming around the world. This technique will allow you to find an around the world path easily. All that you have to do is to transmit a dit, and if you don’t hear it coming back to you, move the beam a few degrees and do it again.
Repeat this procedure, not forgetting to identify as required, until you do hear your signal coming back and have found the around the world circuit path for that direction. Those who scoff need to keep in mind that some operators out there have been doing this for years, only they don’t tell how they consistently snag the rare DX. So if you know of someone who is using only a 2 element beam and working a lot of DX, he could be using a JK Array and not telling.
Diagrams

Figure 1 shows the construction of the two element JK Array and it is just as simple as it looks. This is a top view, with no supporting structures shown, as it is up to you to configure your beam’s mechanical construction.
Measurements
This table will give you the measurements for several sizes for JK arrays. A 10 meter version will work on 6 meters if you can tune it somehow, as the dimensions are close enough to work fine on both bands.
20 meters to 10 meters: dipole length: 33.4 ft. spacing: 8.35 ft.
15 meters: dipole length: 22.2 ft. spacing: 5.57 ft.
10 meters: dipole length: 16.7 ft. spacing: 4.17 ft.
The formulas are: dipole length = 468/F spacing = 117/F
This should allow you do design a JK array for any frequency you want.
THE NEXT ANTENNA is a version of the JK Array that has only been built on a computerized model as far as is known. It differs from the standard array in that it has 5 elements in an X configuration.

Figure 2 is an end view of the antenna. The center element is the reference element and the element to the right is element 2. Element 3 is the top element, element 4 is the one to the left of the drawing and element 5 is on the bottom. Elements 4 and 2 are 180 degrees out of phase with the reference element, element 1. Elements 3 and 5 are in phase with the reference element, element 1. The spacing is still 1/8 wavelength for all elements from element 1. Impedance is unknown, but using either 75 or 300 twinlead and a good coupler, the system could be matched to a 50 ohm transmitter.




Adding the other elements causes the pattern to be narrowed by almost 50% in both the horizontal and vertical planes, resulting in a beamwidth of approximately 30 degrees, with deep nulls to the side. Increasing the frequency to 10 meters from 20 meters causes two small side lobes to spring up at 90 degrees to the major lobes. This would be a monster to construct, as a 20 meter version would take 165 feet of aluminum tubing alone. Five times 33 feet per dipole equals 165 feet. If the CAD polar plots are any indication, it would be a band burner though.
TEN METERS would be a better band for this monster since it would only take 83.5 feet of tubing to build. The supporting structures would be a bit of an engineering project for a 20 meter beam, but it would be interesting to see what this type of antenna would do. Boom lengths for both the super JK Array and the two element version are still under 9 feet. This antenna is an old timer and John Kraus, W8JK, first put it up in January of 1937, and it was an immediate success. Unfortunately, in the passing years, it has not been used by hams too much being over shadowed by log periodics, YAGIs.and cubical quads. It is still a very good antenna and easy to construct. The results from this antenna are excellent versus the low cost of building it in relation to the purchase cost of a triband beam. So gather your materials up and put one up come spring time.
Twin Three Beam
Here is another 1930 era beam that seems to have been ignored in the last few years. It too is a brainchild of W8JK. The difference between this antenna and the JK beam is that the elements are made up of three half wave dipoles spaced 1/6 wavelength. It has the advantages of being broadband in the band for which it was cut. It is easy to match and is very efficient. The modernized version last heard of in the late ’50s used three half wave dipoles spaced 1/6 wavelength and fed with 300 ohm twinlead, and matched with a pair of 1/4 wavelength matching stubs made up of two lengths of 300 ohm twin lead.

The matching stubs are cut using the formula: 234/f * Velocity Factor. Now, finding out the velocity factor of twinlead could be a little difficult as most manufacturers do not list the VF of twinlead since the general ham population does not use it any more. But in the Belden Master Catalog No. 885, all of the vitals are listed, including VF. For the Novice this is a benefit, because all that has to be done is to plug in the figures and do the math.
The pattern of this antenna is a figure 8 but a little narrower than the JK beam, possibly due to the spacing being 1/6 wavelength instead of 1/8, but that is pure speculation. Performance is excellent according to the comments of old timers that have used this beam. This would be a good inexpensive antenna for Novice use. The original antenna was made of wire and hung as high as possible. It could be made into a rotary beam with a little ingenuity.
The only thing to keep in mind is that there must be three dipole elements on each side of this array to keep the impedances in line with the matching network and to keep the feedline impedance in line with that intended to feed the antenna. The original antenna used 600 ohm open line for feedline, and that stuff is as scarce as lower taxes! Spacing of the dipole elements should be not too critical. Anything from 1/2 to 3 inches should do. Elements could be made of 8-foot dowels suitably water and weatherproofed with the dipole elements spaced equidistant around the diameter of a 1-1/4″ or larger dowel and taped or glued in place. The selection of a good quality feedline will lessen the effect of rain and other nasty weather.
Plus a Good Coupler and a Balun
A good antenna coupler will make matching the transmitter easier. The use of a balun at the matching section common point and an antenna coupler would possibly allow the use of 50 ohm coax.
Formulas to be used
468/F = 1/2 wave dipole
156/F = 1/6 wavelength
234/F * VF = 1/4 wavelength stub
The ZL Special

This is another seldom seen antenna with a lot going for it. It is simple and can give about 4 to 7 dB of gain, depending on height, which is a little more than a two element YAGI, but not as good as a three element YAGI. It is also lighter than a YAGI, and can be constructed easier. The original beam was constructed out of bamboo poles clamped to a wooden H frame with elements made out of 300 ohm twinlead and fed as shown on the diagram. The two elements are 180 degrees out of phase which the twist in the element interconnecting twinlead.
ZL3MH Was First
ZL3MH is the ham that put up the first one of these antennas and gets the credit or blame for it. Down through the years, many different versions have been constructed with each design having its followers. All of the designs have one thing in common: one element is longer than the other and it is called a reflector and there is a 180 degree phase shift between the two elements.
The pattern is a cardioid, and has an apparent beamwidth of 40-60 degrees. The feedpoint impedance is anything from 80 to 90 ohms and some people have reported impedances of 70-75 ohms. A simple 1:1 balun would handle matching at the antenna, and a coupler could take care of any left over SWR, if it is enough to worry about. Some hams have not even bothered to use a balun at the feedpoint and have had no problems. The use of some type of balun is recommended though in case of TVI.
Make Ten Meter Version
A ten meter version could be constructed of weatherproofed wooden dowels, or other non-conducting materials as long as they were light and impervious to UV radiation and the weather. In any case, the method of construction is going to be up to the person that wants to put it up.
Easy to Build and Tune
These horizontally phased arrays are a lot easier to build and tune up than a YAGI type antenna. The tuning is done with a yardstick and the surroundings can affect the yagi type antenna more than the phased arrays. The ease of construction and tuning plus the greater bandwidth make the simple phased arrays ideal for those who are looking for an antenna with some gain. Again, careful choices of materials and weatherproofing all connections will result in an antenna that should give good results for a long time.
Formulas to be used
496/F = Reflector length
444.6/F = Driven Element
468/F * .11 = Element Spacing
Shortened ZL Special
The shortened ZL Special came into being when Rolf Shick DL3AO, wanted a beam, but due to the construction of his roof, could not put up a conventional YAGI-type parasitic beam. After seeing the ZL special of DL1CX, he knew he had found what he had been looking for. After some eXperimenting, Rolf found out the elements could be shortened to 3/8 wavelength instead of being 1/2 wavelength with no apparent loss in gain. His antenna weight was only two pounds and could be turned by any currently available TV rotor, of which there were none at that time. He made his antenna out of several pieces of 3/4″ X 1 ” wood and bamboo rods, with 300 ohm twin lead taped to them.

Construction
Modern construction could follow the same route, with fiberglass fishing blanks instead of bamboo poles for the elements that hold up the twinlead. Either construction method would be fine, just remember to weatherproof any wood or other such supporting structures. The twinlead needs to be spaced from the supporting poles if they are wood or bamboo to keep losses from occurring when the elements are rained on or covered with ice or snow. It might be possible to put the elements either inside stiff PVC tubing, or on the outside of the PVC.

If fiberglass rods are used, the twin lead could be either taped or epoxied to the fiberglass rods. In the original article which was published in the July 1959 issue of CQ, Rolf stated that in a test against a three-element beam, the shortened ZL Special was on a par with the three element in 90% of the QSOs. The three element had a better front-to-back ratio, but since the reflector of the ZL Special was only 6% longer than the radiator, Rolf thought that an improvement in the F/B ratio might be had by making the reflector 10 to 12% longer than the radiator. He was unable to continue any experiments due to weather. That is a place too for someone to start experimenting.

Another Beam
Another simple beam came about by accident The wind had destroyed a quad and the owner took the driven element and fastened it to the mast so that, instead of being vertical, the driven element was horizontal. It was bi-directional and had some gain, about 2-dB. The direction of the major lobe was in line with the feedpoint and the side opposite the feedpoint.

Rotary Dipole
The last simple antenna we will discuss is the rotary dipole. This is exactly what it sounds like, a rotating dipole. It is the simplest of all the antennas, and it can be effective when it is used in conjunction with skillful operating techniques. The dipole also has nowhere near the gain that the other antennas have. It is the simplest to construct. It is no more than a dipole mounted on a simple frame clamped to a rotor mast. A balun should be used to take care of the transition from the coax to the antenna. And, that is about all that there is to it.

There are Others
There are other types of simple beams to be found swinging from the masts of hams all over the world, some well known, some not so well known. These examples are the ones that have been around for years. The W8JK array is extremely wide-band, and with an antenna matching unit when made for 20 meters, it will cover everything to 10 meters. The others are mono-band but as light and simple as they are to construct, several mono-band antennas could be stacked on one mast for flexibility.
Last Updated : 25th April 2024