3 elements 'Ubeam' on 40 meters
The idea to build a 40 meters lightweight beam pick-up in my mind when I finished to set up the main tower but in the mean time I was looking for a good antenna on 40.
Why do not interlace 3 elements on the existing 5 els Hygain 205BA ?
The "U" dipole is a wire inserted into the 13 meters element support falling down at the extremes for 3 meters.
Design and modeling
I pick-up in my personal home book library the W2PV Dr. Lawson "Yagi Antenna Design", a milestone in the yagi design. In the last chapter there are many yagi projects, also for 7 mhz.
On the fixed boom length (the Hy-Gain 205 BA boom) 3 elements could be positioned, with good gain and F/B characteristic.
Lightweight was archived with 7 meters fiberglass fish rods that I bought for few euros at a sport megastore. I cannot use the last whip, as it is too thin; so used only 6 meter of it. The two half elements have been joined together with a 2 meters PVC tube, available in the same megastore. Each element use a boom to element plate, aluminum made, with iron u-boalt.
Keep in mind the ratio the W2PV suggest for reflector and director, which is respectly , + 1,49% more, and 4,58% less. Cut all 3 elements wires at maximum length (the reflector lenght). Then tune the radiator for resonance (I use MFJ 259). Recalculate the reflector and the director length with the given percentage and cut them !Performance
I will do shortly better measures using a fields strength meter or a receiver equipped with the Polar Plot software (Web site: http://www.g4hfq.co.uk ).
I received excellent reports from many US and ZL/VK stations and I cannot forgive the long path qsos at 2 pm with W6/W7 at the beginning of the 2006.