I thought this would be easy, but I’ve screwed it up. I’m hoping to get some
insights from this group of antenna experts re the easiest way to proceed!
Perhaps someone could model it for me?
I used the calculator at West Mountain Radio:
http://www.westmountainradio.com/antenna_calculator_zepp.php
Looking for resonance at 10.120mhz. I ordered supplies from Davis RF: their
balanced line / coax center insulator, 14awg solid copperweld and 16awg
19strand copperweld 450 ohm ladder line. I ordered a Balun Designs 4:1 current
balun.
The WMR calculator recommended a matching stub of ladderline 10’ 2.2” and each
leg of the antenna as 61’ 3.1”.
I thought I would add a half wavelength of ladderline to the stub thinking that
this would present the same impedance present at the recommended stub length.
Figuring a .91% velocity factor, I added 44.22’ to the stub for a total ladder
line length of 54’ 5” between the center insulator and the balun. I temporarily
set the antenna legs lengths at 61’ 5” and wound about 18” of overage back on
the antenna wire leg towards the center insulator on each side.
I hoisted this up to about 70’ , pretty much in the clear, other than some pine
branches at each end. 10’ of RG-213 to my RigExpert AA-55 Zoom dangling at
about eye level.
The SWR plot shows a dip at 10.9mhz w SWR of 3.7:1 and a dip at 13.02mhz w
SWR of 2.7:1.
Thanks in advance for any insights!
73,
Ken WC6Y
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