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Old August 19th 06, 02:03 AM posted to rec.radio.amateur.antenna
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Default Johnson KW Matchbox

Will a 50ohm to 112ohm unun current balun on the input side of the
matchbox increase the output capability to handle an open wire fed
80meter dipole at 65' on 40meters? I am 'kinda' stuck with my feedline
length of 80ft, so thought I would raise the input impedance to boost
the output impedance capability. I am aiming for a 1 to 1 'indicated'
VSWR. The differential cap is fully meshed (rotor to top plates) and the
other cap is approx 50% meshed and the matchbox input VSWR is approx 2
to 1.
What say?
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Old August 19th 06, 04:05 AM posted to rec.radio.amateur.antenna
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First recorded activity by RadioBanter: Jul 2006
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Default Johnson KW Matchbox

Bill wrote:
Will a 50ohm to 112ohm unun current balun on the input side of the
matchbox increase the output capability to handle an open wire fed
80meter dipole at 65' on 40meters? I am 'kinda' stuck with my feedline
length of 80ft, so thought I would raise the input impedance to boost
the output impedance capability. I am aiming for a 1 to 1 'indicated'
VSWR. The differential cap is fully meshed (rotor to top plates) and the
other cap is approx 50% meshed and the matchbox input VSWR is approx 2
to 1. What say?


My notuner antenna at http://www.qsl.net/w5dxp/notuner.htm is pretty
close to what you have. Increasing your feedline length to 94-100 ft.
might solve your problem without the unun. The unun actually could
make the problem worse since you don't know if that 2:1 SWR is 100
ohms or 25 ohms or something in between with reactance.
--
73, Cecil http://www.qsl.net/w5dxp
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