W8JI wrote:
>The best case would be a single layer choke that is self-resonant
>on 160 meters. Then you won't need a capacitor, and bandwidth
>will be maximized.
K9RJ's resonant balun is 31 single layer turns (~39 uH) of RG-8A (~13"
long) on ~20" length of 4.5" OD PVC pipe. He uses 81" of RG-8A for the
required C (~200 pF) to resonate the balun at 1830, with the stub folded
inside the PVC being careful not to create a situation where the shield
of the stub could arc through the outer insulation to another conducting
surface. This system worked for a 160 inverted-vee mounted at the 80
foot level on Jim's 100 foot shunt-fed tower and I would imagine it
should work for most typical shunt-fed tower installations on 160. Jim
runs 1500 watts to this balun with no apparent problems. However I'm
also sure Tom's advice regarding the potential fire hazard is important
for anyone trying one of these baluns!
ON4UN confirms that his new book is within a few weeks of release
and you will be able to read more details there. A picture is worth
a thousand words in this case and I'm sorry I can't post Jim's drawing
of his balun. Hopefully this helps for those who are interested.
73, Bill W4ZV
(1" = 1 inch)
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