Here is my own version of my Jpole antenna used in my ham station. Only the half wave radiator was exposed while the remaining quarter wave stub was kept inside on pvc pipe. The pvc pipe prevents rain water from entering the feed point that might affect the vswr of the antenna when raining. It also provides the required structure for our Jpole since this type of antenna works best if kept insulated from the tower.
Several patches of (4" x 1") cartoon or thick cardboard used as spacer in the stub. Keep in mind that the 1 inch spacing of the stub is critical since the stub is actually a ladder line but only shorted at the bottom. Finding the exact position of the feed point is done by trial and error and of course with the aid of your swr meter. After the actual tuning, I found my feed point to be at 0.05 wavelength from the bottom of the stub.The inclusion of the pawsey stub is only my personal preference to minimize feed line radiation but other methods can be used here.
Once completed, secure your Jpole antenna using a pair of scaffolding clamp on the top of your tower. --- 73 de du1vss
