Agree on all of that, which is why I agreed it isn't a dominant effect.
And of course you and K6STI have a good point about the additional wind
loading of mid-element coils.
Every commercial coil loaded shorty-40 antenna that I know of puts the
coils out on the elements, though, so I suspect it may be worth the
bother if done right.
73,
Dave AB7E
On 4/28/2020 10:03 PM, Jim Brown wrote:
On 4/28/2020 6:50 PM, David Gilbert wrote:
Whether NEC accurately models the current isn't the point. You don't
need a model to know that if you push the coil out away from the
center the portion of the current between the coil and the center is
higher than it would be between that same point and the center if the
coil was at the center.
Yes, BUT you DO need a model to QUANTIFY how much better (or worse)
the performance is for variations of a design to answer questions like
"Is it worth the trouble to do all this?" W6GJB and I spent a lot of
time optimzing an 80M vertical for portable operation. We used several
variations of top and bottom capacitive loading combined with several
variations of inductive loading. None of our designs used a base
loading inductor, but we did vary their position. There were some
designs that worked awfully well electrically, but were a problem to
build, or had issues with wind.
And it's also worth it for what you can learn by going through the
process.
73, Jim K9YC
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