"Antonio Vernucci" wrote in
:

Use of fishrod antennas is getting more and more common to cover all
bands 7 ... 28 MHz, including WARC. The typical length of the
radiating wire is about 25 feet, that is about one quarter wavelength
at 10 MHz.

By fishrod antenna, I assume that you mean a telescopic fibreglass pole
of about 10m height, used to support a straight or approximately straight
(including a very coarse pitch helical) vertical wire of the same length.

This has a lot in common with the popular 43' vertical, just the lengths
are different, and the frequency coverage will be different.

The use of a 4:1 balun on all of these things seems inspired by one
antenna manufacturer's recommendation and supply of 4:1 voltage baluns
for the application. Their site shows testimonials, and claims thousands
sold. Eham reviews abound with glowing testimonials.

However... the application of a 4:1 voltage balun seems to me not only to
lack design rationale, but to be quite undesirable in driving common mode
current on the coax feedline, and potentially very lossy in
configurations where the feedline is buried.

I discuss the use of an untuned vertical as a multiband antenna, and
raise the insanity of the voltage balun application at
http://www.vk1od.net/antenna/multiba...ical/index.htm .

Owen