[TowerTalk] Re: Superior 4:1 Baluns

[zl1aih at ihug.co.nz]

Hi Steve,
Can't help you with a distributor or even a manufacturer, but my best home-
brew 4:1 baluns have been those recommended by Roy Lewallen W7EL - 
see the ARRL Antenna Compendium #1, "Baluns: What they do and how 
they do it", particularly pages 163 and 164.
I've built and tested many types of 4:1 balun, air-wound trifilar, bifilar on 
ferrite rod, and toroidal, getting good results with all of them - using an 
antenna analyser, resistive load.   However, using even our modest power 
limit (150 watts) I managed to smoke most of them when the loads were 
reactive, which is most of the time.   The only one that didn't fail (or even get 
warm) was W7EL's 4:1 current balun.   
Using only RG-58 on two 4" diameter PVC waste pipe formers, placed at 
right angles to each other, I coupled a 300' run of nominal 600 ohm line to 50 
ohm coax at the base of a 60' tower, to feed a Force 12 C3 - this was after 
melting the insulation on the windings of several different baluns.
Adding the 40 meter dipole to make a C4, I used two separate W7EL baluns 
and a large relay to select the appropriate baluns - the 20/15/10 unit is 4 
turns of RG-213 on two 6" diameter forms, and the 40 meter balun is 6 turns, 
same arrangement.   Most important to place the formers at 90 degrees.
At the shack end, I've tried balanced 'L' network tuners with baluns on either 
input or output sides - best results for me, measured by both antenna current 
in the 600 ohm line and field strength at   >1 wavelength from the antenna is 
the old balanced tuner, or a borrowed Johnson Matchbox which gave the 
same results.
73,
Ken ZL1AIH