![]() ![]() The DL6WU design is well known and used mainly for long Yagi's with 10 elements or more, but small designs still work well. The Yagi is a DL6WU design calculated with the excellent software by VK5DJ. 8 turns is more than enough for VHF! The antenna would probably perform fine without it, or with just a few turns. The driven elements are made from 4mm aluminium solid rod, so that they fit inside the terminal connectors.Ī coax choke was made by winding 8 turns of coax around the boom between the feed point and BNC connector. More detail of this can be seen in the photos below. The copper was then screwed and glued to the boom and plexiglass and the coax was connected to the copper via solder tags. A strip of copper was cut from some 15mm copper water pipe and brass connectors from a terminal block were soldered to it. This was done by cutting a slot through the boom and inserting a piece of plexiglass. The problem was that the driven element has to be two separate elements and therefore can't really be slid through the boom like the directors and reflector. A gamma match might have been an option, but I decided to go with the basic open dipole driven element. Due to the need for this antenna to be portable, a folded dipole was not really an option. Yagi antennas that I have built in the past have used folded dipoles and a 4:1 coax balun. ![]() The driven element was the most tricky part to design. A pillar drill is handy for this, if you have access to one. The most difficult part here is drilling the holes perfectly, so that the element is 90° to the boom and all elements are in line. The reflector and directors are made from 6mm aluminium tubing and pass through holes drilled in the boom, with a small cable tie super glued on the elements to provide an 'insert to' stop, in order to centralise the elements (see photos below). ![]() I used 32mm solvent weld waste pipe for the boom, with a screw access plug on the end, so that the end can be unscrewed and the elements can then all be stored inside the boom. With that chosen, the next problem was how to build it so it can be put together quickly. 5 elements was chosen, as the boom length is 1.5m (5ft) which keeps it portable. The challenge for this antenna was that it had to be compact enough to walk up a mountain and be quick and easy to assemble and disassemble. I had previously made some Yagi antennas for amateur satellite use and also for WiFi and these had all performed well. I made this antenna in 2008 for our first SOTA activation in the Lake District. Since this antenna was shown in the July 2011 edition of RadCom, a few people have contacted me asking for some information on how it was constructed. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. Archives
June 2023
Categories |