The vertical members are 2ft pieces of 1 1/2 inch weld-able angel iron available from building supply stores. The weld-able grade was chosen as it is the highest grade of readily available retail OTC steel. I bought a 4ft piece and cut in in half. Mirror images were constructed. The angles are held to the 4x4 with 3/8" grade #8 bolts. There are 1/4 #8 compression bolts that cross the holes made the 3/8" bolts. These are visible in the picture as the bolts with the large 2" fender washers.
I drilled the holes at the center line of the 4x4. I found it important to keep all holes on the angle co-linear. It makes centering and drilling much easier.
The white plastic part is a 2" PVC compression coupling. Its diameter is 3.5" which is exactly the diameter of the 4x4. This coupling allows for a very nice tight fit between the angles. The coupling is held to the angles with 3/8" stainless bolts one through the top compression joint and the other through the bottom compression joint. Inside the compression joint is a piece of 2" schedule 40 PVC which acts as a spacer its length is slightly longer than the compression fitting. This piece is just visible at the top and bottom of the fitting, and is the part which the Aluminum tubing sits.. Inside the schedule 40 is a 2ft piece of fiberglass. It is 2" in diameter and gives a nice tight fit to the inside diameter of the Aluminum tubing. The bottom of the fiberglass is flush with the bottom of the schedule 40 spacer. The fiberglass extends about 15 inches above the top of the spacer and sits inside the Aluminum tubing. The coupling/spacer/fiberglass is drilled through and through. The bottom bolt is the hinge and the top bolt is the pin which locks the antenna vertical.
