On 11/12/2010 4:22 PM, Stuart Rohre wrote:
Most external baluns are of heavier construction and therefore lower
loss potentially, than built in baluns common to 1970's tuner designs.
Loss in ferrite chokes and in baluns wound with ferrites is NOT a
function of HEAVY construction, but depends primarily on the
characteristics of the ferrite material (the MIX), how the chokes are
wound (mostly the number of turns), and the size of the core.
Likewise, HEATING in the core depends on the loss, the TX power level,
the balance of the antenna, AND the length of the transmission line into
which it is inserted. Using a balun on Field Day (usually 100W) and
saying it worked fine doesn't mean much. A FAR better test would be
running 1.5kW through it into difficult lengths of line and with an
unbalanced antenna (like a Windom) and noting whether or not it got hot.
Although I own and love a half dozen Ten Tec tuners, I don't use
twinlead, so I've never given the balun a torture test. :)
73, Jim K9YC
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