On Tuesday, 28 June 2011 11:21:50 UTC+10, Wayne wrote:
I have seen two commercial antennas advertised that are each 43 feet tall,
and have no traps/stubs, etc.
There appears to be a 4:1 balun at the feedpoint. Mentioned, is the
requirement to have a tuner at the driving end of the feedline, and max
VSWRs in the 4:1 range.

Several manufacturers supplied and recommended a 4:1 voltage balun at the feed point of their 43' unloaded vertical. It would seem driven by one seller, and a mob of sheep following.

If you look on eHam at the evaluations of the configuration, you will find that most reviewers thought it a great antenna system.

I commented on that in some web articles and many postings in online forums over years. My thoughts in seeking an understanding of how it "works" are in the article at http://www.vk1od.net/balun/application/Z5.html .

I should note that after a particularly vigorous discussion in one forum a year of two back, one of the sellers changed his recommendation to an unun and advised existing owners how to modify their balun to an unun. The method was quite the same as I previously documented at http://vk1od.net/antenna/multibandunloadedvertical/ .

The whole saga reminds us that anything "works", and flexible sellers remain poised to supply to the current fashion.

Owen