On 21 Mar 2006 19:41:42 -0800, "RHF"
wrote:


SO HERE WE GO AGAIN - - - - - - - - - - - - - -
This is a Three Band : 49 & 31 & 22 Meter Bands
Shortwave Listener (SWL) "Receive Only" Tri-Band
Dipole {Wire} Antenna built on a On-the-Fence
Question What Do We Do To Make It 'perfrom' ? ? ?
? To Perform - Or Not To Perform - - - Is That a Question ?
A little better across the Shortwave Bands so we can
"HEAR" a little of everything from 1.8 MHz to 30 MHz.
Not a good answer but never the less a fair answer is
the 4:1 Balun to 'smooth-out' the impedance mismatches
from the Three (3) Dipole Antenna Elements and provide
a fair 'match' from the three of them across the Shortwave
Bands; know that they are One-Foot, Three-Feet and
Five-Feet above the ground when Idealy they would be :
49m = 38.5 Feet above AGL
31m = 24.5 Feet above AGL
22m = 17.1 Feet above AGL

alas - it is an imperfect world - iane ~ RHF
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I took into consideraton that there are three dipoles here, connected
to a single transmission line -- so hopefully each will be within
yelling distance, impedance wise, of 75 ohms, so there's no need for a
4-1 balun to a 50 ohm input.

Unless you want to transpose 75 ohms to about 20 ohms?

And if the antenna is less than a half-wavelength high at frequency,
on a fence so to speak, the impedance could be anywhere between 40 and
90 ohms, according to chap. 20 of the ARRL handbook. Still no need for
a 4-1 balun. Maybe a 1 to 1 choke balun, to sop up noise, but a 4-1?

What is it, this high religious SW fever for baluns in this group :-)

bob
k5qwg