Just some 'food for thought' for those out there using 160m dipoles fed with
open wire so they can use the antennas on the other low bands.
Until recently, I used a similar arrangement until I finally got up a good
seperate antennas for 80m. At this point, I junked the open wire (about 60'
in total), commercial T-match ATU (plus balun) and put RG58 coaxial cable
and a choke balun on instead. The difference was quite startling - about 1
'S' point improvement in my 160m signal.
The open wire was home made, using beverage (drinks) tubing and, latterly,
commercially made spreaders. As open wire goes, it was great stuff and
noticeably better in performance than good quality 300 ohm ribbon.
I used a variety of ATUs on the dipole/open wire, including a balanced
parallel tuned ATU (link coupled) and commercial T-match minus the balun and
the performances were all about the same. I also tuned the T-match in the
recommended fashion to use as little of the inductor as possible.
It was only when I junked ATUs and open wire all together that things
improved - the old hands who say avoid inductors in 160m ATUs/antennas are
right. One of the VK6 160m gang here thought I had bought some kind of super
linear when I changed to the dipole with co-ax feed!!
For those who like to use their 160m dipoles on 80/40m, it perhaps might be
interesting to see how parallel dipoles for 160/80/40m with a choke balun
and co-ax feed go at your QTH, rather than using open wire feed. On the
other hand, maybe you have a very low loss ATU...or do you?
73,
Steve, VK6VZ
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