Someone asked me the other day, why I chose to use open wire feed lines instead of coaxial cables. I didn’t answer that question very well so I thought I would make a diary entry here and put the reasons in written form.
- First; the physical and cultural needs of my neighborhood dictate a low profile antenna presence. That to me implies a single non obtrusive structure preferably obscured by trees and foliage. Yes, I could move but there are other factors such as my wife and son and twenty years of history that take precedence over Ham Radio.
- Secondly, I am old and not getting any younger. That to me says my antenna needs to be reliable. Reliability means not complicated with things that break high in the sky because getting a work party together is increasingly difficult and I cannot do this task myself.
- Next, it seems to me that a lot of gimmickry is applied to antenna designs in order to facilitate coaxial cables. This includes traps, coils, stubs etc. etc. that add complexity to an already unwelcome neighborhood accessory. It also happens that those “Fixes”, while designed to accommodate coaxial cable, also introduce loss elements into the antenna that a simpler antenna would be free from.
- My choice in antennas is simple and uncomplicated. It is a 2 wire dipole, each half 25 feet long and made of 105 strand insulated 10 AWG strung along a pair of 20 foot long fiberglass fish poles atop a light and guyed aluminum tube mast. It stands at 27 feet and is threaded through some trees to keep visibility low. Lengths chosen mean I have 5 feet on each end dangling vertical. This was intentionally added to tame feed point impedance excursions.
- So that I can work as many bands as possible, I have chosen to feed this dipole with open wire line of my own making. It too, is robust and consists of a pair of wires made from .125 inch phosphor-bronze wire rope. I believe this is a very low loss solution, even while working with radical feed point impedances encountered while using non resonant antennas much shorter that required to normally operate on say a low band. Likewise I carefully chose my tuner to be of high quality and low loss with good robust components.
- This combination of large conductors and open wire line transmission line afford me a very efficient solution with minimum visual impact and most importantly, cover a lot of bands efficiently.
There it is in a nutshell and I hope is helpful should the gentleman happen across my blog.
Thanks for reading my Blog. Best, Chas W5PG