Re: More QRO secrets revealed.... 15 -20 kw baluns !!
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> The boys on the contest reflector finally figured out the same
thing. The typ W2DU baluns using 303 teflon coax.. and the
tiny type 75
beads would heat up with just a 500 w dead cxr on
all bands from 1.8 to 30
mhz. They switched to type 43
small beads... and the same small 303 teflon
coax.[slightly
longer.. more beads] They ran the exact same test as b4.....
except 2200 watts.... zero heat ! ..."
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Jim, I like?air wound baluns best.? But
as you point out, the geometries can oftentimes get in the way.? In the
alternative, I have successfully used a combination of #43 and #77 material on
RG-214.? The #43 material is used on the ends with #77 beads sandwiched in
between over a distance of ~ 60 inches.?That can create some weight and
manipulation problems too.? In that case, it's tough to beat the W1JR or
W2FMI technique of winding RG-303 (at 1.5KW level) onto large?#31 mix
cores.? I believe the DX-Engineering baluns are constructed this way.?
?
Paul, W9AC
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