Yesterday, I measured the current distribution on my
550 ft beverages. The near end/far end current ratio
was 5 dB on 160m gradually increasing to 10 dB on 40m.
It seems to me that, at 550 ft, I have already reached
the point of diminishing returns on beverage length,
and that on 40/80 meters, I might very well want
to go down to 300 feet or so. It didn't make any
significant difference when I changed the height from
2 feet to 5 feet. Anyone have any thoughts on this?
BTW, these beverages were outstanding in the heavy
QRN yesterday. They were even a big help working
Europe on 30m. So, whatever the current distribution,
they hear well, at least.
(Experimental details: I used one of those clamp-on
RFI cores for line cords that opens up like a clam
shell. I put 5 turns on the secondary (the beverage
itself being a 1 turn primary). Primary impedance
was about 3 ohms on 160m; should be negligible.
Besides both ends, I also checked at 1/4, 1/2 and 3/4
points on beverage, and current linearly tapered off
apparently no standing waves to speak off.)
richard@karlquist.com
www.karlquist.com
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