A tube-Yagi for portable work on 144MHz

摘要

A 177cm length of 19mm diameter plastic waste water pipe was used as the boom for the tube-Yagi. This needs to be carefully marked and drilled to make sure the elements will be parallel when they are inserted. Start off by drawing a straight line down the tube. There might be a seam on the tube that you can use, otherwise try laying it on a flat surface and run a marker pen alongside using the surface as a guide. Next, wrap a piece of paper around the tube and use the straight edge as a guide to mark an accurate circle around the tube where the elements will go. Then cut the paper to the length of the circumference and find the halfway mark. By aligning one end of the paper with the line, the middle point will act as a marker for the holes on the other side of the boom. Don't try to drill through the whole boom in one go. Instead, drill the two holes separately. In this way you can correctly mark out, and then drill, the 10 holes on the boom that will take the five elements. You might need to open up the holes a tiny amount, but try to make the fit tight enough so that the elements elide in with a little friction.