On 5/11/2022 10:20 PM, Jim Brown wrote:
Low dipoles are closer to 50 ohms, high dipoles are closer to 75 ohms.
Low would be much less than a quarter wave, high would be much more than
a quarter wave.
BTW -- there are a couple of very useful graphics that help understand
this at the beginning of Chapter 8 of ON4UN's "Low Band DXing," another
great antenna book published by ARRL. One shows the ground reflection
as a mirror, the other, paragraph 1.3.1 in my 20 year old edition, shows
how feedpoint R and X vary with height for an 80M dipole. Ground
conductivity is not shown, so I'm guessing it's computed for average
ground.
And I agree with W4TV about the usefulness of the Antenna Book. I
contribute both to it and to the Handbook. These three ARRL books have
been central to my learning, in some ways, at least as important as my
EE education.
73, Jim K9YC
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