I made the 2el ZLspecial antenna at the same time as the QRP NO1transceiver in 1988. It was using it in the condition of 2el for a while. But, feeling the want of ability in 2el. I did the remodeling to 3el due to the performance up in 1993.
The beginning was making the ZLspecial antenna while seeing the data of the antenna handbook. However, I am making the antenna while using this MMPC after it, because I got antenna calculation software MMPC in 1994. ( this software MMPC was made by Mr. Matsuda JA1WXB )
*The paint image that is using it with this corner is the thing that Kikuchi OM (JA1HWO) made.
It explains about the way of making a 2el ZLspecial antenna here. Also. I am introducing it regarding the remodeling method from 2el to 3el in the next clause.
The measure of every part of the 2el ZLspecial is as the above figure. Ribbon feeder of 300 ohm is used for all the elements.
The structure of 2ELZLspecial is easy. However there is the front gain of about 4db. This antenna is the antenna of the type HB9CV. The front gain is bigger than 2EL Yagi antenna.
Although the aluminum pipe is used for the element in a usual antenna, Ribbon feeder of 300ohm is used for the element in this ZLspecial.
Structurally, Ribbon feeder of 300ohm is processed like a rough sketch. In this case, specified performance is not obtained when you make length halfheartedly. If you make it correctly with the measure of the drawing, especially it needs not to adjust it.
To, broaching the vinyl chloride pipe of the inside diameter of 25 mm with the measure of the rough sketch assemble it to the H form. It fixes it firmly so as not to come off to, by using the glue for the vinyl chloride pipe.
The fishing rod made of fiberglass is attached in 4 top of the vinyl chloride pipes type of H form. At this time it adjusts it to wind the vinyl tape to the root part of the fishing rod several times and enter suited into the vinyl chloride pipe.
Winding the vinyl tape to the difference in level part of joining department it fixes it so as not to come off. A fishing rod uses the one that are the length of 4.5 m. Yet a thin part cuts and do not use it.
The assembly fixes the element that I made with the preceding clause. A vinyl tape is used for the fixation of an element. Vinyl tape for the fixation is the interval of about 20 cm.
The ZLspecial antenna is the balance style antenna of a right and left symmetry. On the other hand, the coaxial cable that connects is imbalance structurally. It is the role of BALUN to mediate these for both.
Also, the impedance of the 2el ZLspecial is about 90ohm. Feeder that connects to this uses the coaxial cable of 50ohm generally. When it connects as it is it becomes (high condition SWR) mistake matching. It becomes a matching circuit (the right side of a rough sketch) to revise the difference of this impedance.
I explain it about BALUN and matching circuit in this clause. The concrete preparation method is as a rough sketch. When the 75ohm coaxial cable is used for feeder use only BALAN. Also, both of BALUN and matching transformers are necessary, when you use the 50ohm coaxial cable.
Because the boom part is a vinyl chloride pipe I am hanging it with the nylon rope like the drawing due to reinforcement.
It is not a big problem, even if it does not hang the antenna with the nylon rope, because antenna itself is light.
By adding 1 element (Director) to the 2el ZLspecial you are able to convert it into the 3el ZLspecial.
The front gain becomes the gain up of about plus 3dB on calculation in comparison with 2el. A beam pattern becomes narrow toward a front at the same time as, a gain up and the performance as the beam antenna is improved substantially.
I suggest that I convert into 3el by all means, if there is a margin in the establishment space, although the difficult point is that antenna itself becomes big.
Remodeling utilizes 2el that produced it with the preceding clause as it is and make. In this case, only a few of reflector needs to make it short. I am explaining the length of reflector of 3el with the next clause.
The measure of every part of 3el ZLspecial is as a rough sketch. It becomes the wide space type that takes the interval of director and radiator widely, to take the front gain largely. The rough sketch is the measure figure of a wide space antenna.
The 2el part changes the length of reflector the 6.85m to 6.61m, although 2el ZLspecial uses it as it is.
The front gain and F/B ratio of the antenna are the calculation result of antenna calculation software MMPC whichever.
The figure of under is 3el ZLspecial in appearance from the side. The part that becomes a boom is using the metal pipe of diameter 30 mm.
It fixes it with Cramp with the feeling that suspends ZLspecial of 2el to this boom. The condition where it was fixed can see even the photograph of the next clause.
Make Director with the next method. First attach 2 fishing rods to the vinyl chloride pipe of the length of 50 cm. Next make the element with feeder of 300ohm of the length of 6.15 m. At this time I do both ends of the feeder the shortstop. Fixing this element in the fishing rod in the interval about 20 cm it is completion.
When it attaches director that was completed in the position of 2.8 m from 2elZLspecial it becomes 3elZLspecial
The photograph of under is the arrangement situation of BALUN and also matching transformer. you can see even the situation that is attaching 2el ZLspecial, to the boom of the metal pipe with cramp.
It is thought that each characteristic of the antenna that was completed be as follows. The left side of the figure of under is the beam pattern of 2el. Also, the right side is the beam pattern of 3el. These 2 pieces are the one that antenna calculation software MMPC of Mr. Matsuda (JA1WXB) calculates and output.
The SWR characteristic and also measurement pattern of the figure of under are the thing of 3el ZLspecial that I made. I measured SWR measurement by using measuring device RF-1 made in America.
With RF1 during the measurement of SWR ---- SWR measurement characteristic
measurement pattern figure (gif 20kb)
Measurement pattern figure is seen