(Continued from Part 1. This concludes the article.)
Rugged Construction
Given the materials at hand. and the other design goals, it was easier for me to produce a yagi antenna for UHF frequencies than a comparable moxon antenna. The build had to be durable, and not likely damaged by abuse or neglect in a chaotic environment. And it can be easily repaired in the field. Not ‘mil-spec’, but close enough. And consider that UHF is easier to contain in a valley that has a pine forest, so it is therefore less of a COMSEC problem when low power is used. And to keep costs contained, and production possible in an austere environment, using common scrap materials that are the lowest in cost, ease of manufacture, helps makes the build a sturdier yagi that performs predictably at UHF frequencies than a UHF moxon built with the same or similar materials. And the EWB yagi significantly exceeds the wide-band attributes of the moxon.
Adequately Compact for Portable Work
While 1/3 larger in size, in comparison to a moxon, it still acceptably compact and rugged enough to be used as a portable, or at a base station antenna. And it duplicates the wider RF footprint that makes it easier to use as a part of a community communication effort. A narrow RF footprint can be too narrow and difficult to point, whereas the larger RF footprint can include several stations, and yet be pointed away from a station.
If I were using GMRS for a security operation, I would prefer to use a 5-element (or more) yagi that not only has a narrower footprint. But more importantly, because it has a higher front-to-back (F/B) ratio that sends more of the RF forward, and less to the rear. Yet a 3 element yagi has a suitable RF footprint for my AO, and is the superior choice over an onmi-directional antenna for such purpose. And as I mentioned before, it can be used horizontally polarized to reduce (attenuate) the signal that goes out the back to nearly match the moxon F/B ratio, should the moxon be vertically polarized.
The EWB yagi is an attempt to engineer a good all-around tool, and engineering anything is a series of compromises that hopefully results in a balance of attributes that produces a tool that meets a design goal. It has got to be practical. I’m not an RF engineer, but I do like making stuff work.Continue reading“Building a EWB/UHF Yagi – Part 2, by Tunnel Rabbit”