A peak of Cycle 23 has going away, I had decided to change my antenna system. I had used Grand plane antenna. When I participated in a big pile-up, especially in SSB mode, I became often sad. I wanted a beam antenna, but I had no idea to build a tower then. As you know, a house is small and its site is also narrow in the residential section in Japan.
I had found the article of delta loop antenna reported by JJ1VKL in CQ ham radio Sep. 2000 Japan.
built up this antenna in October 2000. The rate of call back became higher, although I don’t know the beam pattern of this antenna. I think this antenna has better beam pattern than Dipole antennas especially in high bands.
This antenna is consisted with 2 fishing rods(7.2 meters), 1mm enameled wire and ICOM AH-4 antenna tuner.
V element part is a fishing rod. We could not find pure glass fiber rods in Japan. A selling rod almost consists with some Carbon fiber. The rod I purchased, is 7.2m and consists with 37% of Carbon. I reinforced connecting points with cyano-acrylate glue and I covered the rods by aluminum tape with adhesive (width 75mm) longitudinally. Spiral taping is not so good.
If the rod material is pure grass fiber or non-conducting one as like as a bamboo or wood, you can use a vinyl coated or enameled wire and it would be attached to the rod as an element.
In the case of single band delta loop antenna, the best circumference length is one wave length.
In this antenna system, for HF multi-band use, the better length of circumference may be at least 15-20m. If the length is near to 1 wave length, a beam pattern will be kept better. The Circ. length is getting shorter and shorter than 1 wave length, the beam pattern is getting more loose and loose for example on 80m, 40m, 30m band.
Late Problems
Degradation of aluminum tape has progressed.
I did the maintenance of the main rod half year later.
Tinned wire was attached to rod with insu-rock ties every 30-40cm.
1. Chemical reaction causes surface degradation = rusty change
2. Mechanical force by wind causes cracks of Aluminum tape as you can see in a picture
Main rods are supported by IRECTOR PIPE SYSTEM. I got it at DIY shop. The Diameter of IRECTOR PIPE SYSTEM is 27.5mm.
Connection of rod and IRECTOR pipe is reinforced by INSU-ROCK tie. Connecting parts of IRECTOR pipe to pipe are also reinforced by 3mm screw and nut.
The antenna tuner is ICOM AH-4. I use hose-pipe-bands (metal) and a vinyl wire to connect between rods and the tuner. A vinyl wire is soldered to a hose-pipe-band. One side element connects to ANT. terminal and another side element connects to GRND. terminal of AH-4.
The 30cm base-end of rod is not wrapped with aluminum tape. The coaxial cable 5D-2V turns 8 times to FT-240 #43 (Ferrite Core), the tuner control cable turns 6 times to FT-140 # 43.
How to connect rod element and horizontal wire :
3mm*20cm CREMONA rope was added to a rod tip, 5cm of a 20cm rope end covered a rod tip and fixed with Epoxy bond and its base is shaped like a ball ( short pot life time (1-5 min) bond recommended .) This is to prevent to never pull out the twisted enamel wire as mentioned next. Aluminum taping is stopped just it. The diameter of using enameled wire is first 0.8 and now 1mm. I remove enamel about 15cm of a 30cm wire and twisted it about 20times around the aluminum tape section of rod tip, and wrapped with self adhesive sealing tape. Bi-lateral end of Horizontal enameled wire is twisted with other two 20 cm enameled wires like as a picture. Horizontal and rod tip wire is connected using terminal connector for a car electric circuit use.
Length of the Horizontal enameled wire is 8 meters.
Main rod is strong for wind, but wire connecting portions are weak point. The enameled wire is cut down by wind at this area. I should remake a wire element 1 or 2 times during one year. I think that connecting portion would be made more straight and shorter and/or I would use thicker wire. If the wire is thicker, a case of rod tip breaking may be higher.
At my location, The wind speed is often over 10-15m/s in winter season.
references :
164-165, July 1999. CQ ham radio.?JJ1VKL?Haraoka
228-237, April 2000. CQ ham radio.?JH1GNU?Kobayashi
Article origiannly available at http://www.geocities.jp/yoshiki_ja/deltae.htm