The double zepp looks to me like a dipole fed with balanced line. What
is the advantage to this antenna?
John KK9A
Ken Bauer WC6Y
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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