steve at karinya.net
Sun Feb 1 09:57:12 EST 2009
Interestingly, it isn't always true that running the ladder line all the
way is lower loss than using coax for part of the run.
Take the G5RV on 80m. At the end of the usual 30 odd feet of ladder line
the impedance is about 14-j1. Any further length needed to get to the
shack would be lower loss using RG213 with a 3.6:1 VSWR than 450 ohm
line with a 32:1 VSWR.
Where circumstances allow, I see nothing wrong with choosing a
combination of wire length and feeder length which results in "benign"
impedances, either directly at the tuner or for minimising the loss in
any further short length of coax. Actually, the G5RV isn't very good in
this respect. The ZS6BKW is much better; with a 93ft "top" and 44 ft of
450 ohm line it delivers a 50 ohm VSWR under 2:1 on 5 bands - 40m, 20m,
17m, 12m, and 10m.
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