Extended Yagi mast for SOTA

One of the activities I enjoy with Amateur radio is climbing a summit and operating in the Summits on the Air program. Climbing summits has gotten harder as time progressed and I am doing less of it now but I still enjoy getting out and activating some lower summits. For my hill-top activations I would use my mobile VHF equipment. This works for me as the mountains I could climb were all scattered around the edge of the Fraser Valley and Victoria areas. From the summit looking down on the valley my 2m radio and 4 element yagi antenna works very well and I have made contacts as far as Mount Rainier near Seattle.

Over the years of using the yagi I have slowly improved my set up. Currently I would use one of my ski poles as a mast, fit a PVC pipe over the handle which supports the yagi’s boom. Then I could drive the point of the ski pole/walking stick into the ground and have a reasonably stable and directional mast. It works quite well but… The tips of the yagi elements were quite close to the ground and as such ground losses and pattern interference was significant. I needed to raise the yagi up higher. Often I would mount it in a tree if one was handy. Since I generally had two poles with me I thought of attaching them together to get a double high mast out of them.  That extra height would eliminate the worst of the ground proximity effects.

My initial method of combining the two poles was to tie the one to the top of the other. It was a cumbersome process and generally left me with a very unstable mast. I migrated to using stiff pipe-cleaner type ties and these held better but the angles were not straight and if I rotated the combined unit, it would often pull apart. Eventually it dawned on me that I had a 3d printer and had already made a mast holder for my HF gear why not design and build a joiner for the two poles. 

My concept was simple, copy the size of the PVC pipe holding the boom to the mast and attach two rings on the side to hold the pointed portion of the stick that would be on top. It was a simple enough concept and I quickly constructed a simple program in the OpenSCAD modelling language to produce the joiner piece. Once designed, I copied the model to my printer slicer program and decided to try a test run using basic pla plastic and then after refinements reprint it in a stronger plastic. I printed the piece and tried it on the poles. It fit perfectly; no adjustments would be needed. Rather than just discard the prototype unit I decided to just use it until it breaks and then print a stronger one. I am now waiting for my next summit and chance to try it in the field.