I used aluminum welding rods to build the 3 Element Light weight yagi. The welding rods are 1/8” X 36”. You will have to join two rods together to make an element. That was a problem, I decided to use a mechanical joint. I found some 5/32” brass tubing at the hobby store that fit perfectly. There is a problem on how to cut the brass tubes without distorting it. I asked a ham friend that does radio controlled planes on how to do it. He suggested that I use a Dremel with a cut-off blade. It worked great. I first make the elements. The Reflector and Director are easy, just join two welding rods together with a brass tubing. I crimp the brass tubing connection using a High Sierra coax connector crimper (it is just the right size). Measure from the middle of the brass tubing to each end and cut. Save the cut-off as they are long enough to make elements for 70cm.
I use 3/4” conduit fitting for mounting the elements. I drilled a hole with a #21 drill bit. The brass tubing will be a tight fit. You can get the conduit fitting at Lowe’s for $.54. See conduit fitting below.
Using the Table above mark a 3/4” PVC pipe for the elements. Mount the elements on the pipe. Use 8x24x1 1/4” bolts to secure the conduit fittings/elements to the boom. Prepare a piece of coax (RG-8X). Take off the insulation (1 1/2”) separate the shield and the center conductor. Sand the brass tubing on the driver element on each side of the conduit fitting. Route the coax back from the Driven element back towards the Reflector (longest element). Solder the braid and the center coax to the driven element on east side of the conduit fitting. I model the antenna in EZNEC at 10’ height and medium ground - see plots below.
Conduit Fitting - Driven Element
Finished 3 Element Yagi - Light - without coax
Finished 3 Element Yagi - Light - Mounted Horizontally
We measured the SWR on the antenna we built, it was a little different than the model. At 144 it was 1.3, at 146 it was 1.2, and at 148 it was 1.6. Good across the entire 2M band.