All my lower band Yagis (50, 144, 222 MHz) are built on 1 inch square aluminum tubing (plentiful in hardware stores around here). I drilled holes through the tubing to clear the 3/16" diameter aluminum elements. The elements contact the aluminum boom (non-insulated). I used element lengths from a table in some VHF book that gave lengths of the elements for insulated and non-insulated elements (they are slightly different). Each of the elements is held in with a screw on the side of the boom parallel to the elements. The screws are perpendicular to the elements. I use a T match to feed them. I mounted a piece of 1/4" thick acrylic to the boom at the appropriate location with screws and mounted the elements of the T match on the other side. The elements themselves are 1/4" brass tubing and they are tuned with sections of 1/8" diameter solid brass rod. I approximated the dimensions in this article:
The 432 Yagi is similar but I used 3/4" diameter round aluminum tubing. The driven element passes through a larger hole through the boom with the element passing through a piece of teflon tubing with the ID being the diameter of the element (1/4" brass tubing) and the OD being the diameter of the hole through the boom.
73, Zack W9SZ
