The JP1QEC Garden Beam SOTA Antenna

sota japan

Japan is blessed with many mountains and for many hams this means SOTA. Summits on the Air is wonderful for those that want to combine hiking and ham radio in a single activity. The Yaesu FT-817 is a popular radio for this activity. Japan has thousands of SOTA summits to be activated. Ontario has practically none.

I have been communicating back and forth with Akira Motohashi JP1QEC (http://qrz.com/db/JP1QEC) . Akira-san is an active SOTA expert and has created an interesting antenna concept. It is a 2 element vertical beam for 20m that uses a passive reflector element. It is light and compact and easily deployed to provide some gain and directivity to mountain top activity.

He tested it during his JA/ST-017 summit of Mt Minoyama

I made a quick and dirty 10m version as a Proof of Concept and using a Field Strength Meter does show some directivity as designed. I plan to make a proper 20m version for field work with my QRP radios and for Field day use. I am trying to decide if I use #26 silky wire or #18 for more strength. I have made some translations and look forward to more new antenna designs from Akira-san and more SOTA JP activity.

The GardemBeam-QEC details are as follows:

(1)   Wire length and arrangement

qec1

The lengths indicated must be multiplied by 0.96 for the reducing coefficient. The 50 ohm coax cable connects directly to the Feeding point as in the figure. The center conductor of the coax is connected to the vertical wire element that is 5.14m. This is the radiator.

The coax shield is connected to the wire that is 5.7m, and to another counter poise. The counter poise is made of the same kind of wire, and length is about 4.4m. I recommend to make 2 wires or more.

The 5.7m wire and the 5.29m (Passive Reflector) wire are connected at the bending point.

The calculations are for a total length of 5.29mX0.96+5.7=10.7m i, the bend is at 5.7m. 5.7m is the actual  distance between the radiator and reflector. This 5.7m spacing is equivalent to the spacing of a boom on a  YAGI.

(2) Beam pattern calculated by MMANA-GAL

qec2

 

This isthea frequency dependency of the calculated SWR by MMANA-GAL. It could be a little high, but this is a reasonable value, I think.

(3) Finally, the total shape with the counter poise

qec3

In this figure, counter poise were attached to both feeding point and bend point. But, I always am using GardenBeam-QEC without one at the bending point.

If you look at the design you can see Akira has a wire coounterpoise that connects to the radiator insulator that he has homebrwed.

A way of setting of this antenna on the mountain.

(A) Tips of Radiator and Reflector are connected to  thin ropes that are 10m long

(B) A plastic bottle filled water is tied to the another tip of the rope.

(C) Throw the bottle up to the tree branch.

(D) Pull the rope and stretch the element.

qec7qec6p8p6p3p2p1

Go out and make some contacts

 

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