Topband: Cushcraft MA-160v
Roger D Johnson
n1rj at adelphia.net
Thu Feb 22 12:49:47 EST 2007
I've seen several questions about this antenna lately.
I modeled it for a VE using EZNEC4. I worked from the
CC instruction manual so my dimensions might be off
a bit but I'm sure I'm in the ballpark. EZNEC shows a
feedpoint R of just under 10 Ohms at resonance. This
means that, if you follow the instructions and add
radials for a 1-1 SWR, the ground R will be 40 Ohms!
The efficiency under these conditions will be about 20%!
If you go to a more robust ground radial system, the
feed R will continue to decrease as the ground R becomes
lower. Of course, the feed R will drop below 50 Ohms so
a matching network will probably be necessary. Another
consequence of a good ground system is a narrow bandwidth.
The antenna will probably be a decent performer over a
good low resistance radial system.
Remember the USS Liberty (AGTR-5)
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