[TowerTalk] Good vacation antenna

[David Gilbert]

Because whatever current is left after the loss in the tuner still makes 
it to the antenna but doesn't have a major portion of it compressed 
inside the coil where it matches and also suffers loss but doesn't 
radiate.  Radiated RF is a function of BOTH current and length.  If it 
was otherwise we'd all be using parallel tuned circuits with large coils 
on 40m instead of aluminum tubes and wires.

Dave   AB7E





On 7/3/2025 2:11 PM, Wes Stewart via TowerTalk wrote:
>    So you move the loading coil from the base of the antenna to inside the tuner in the radio (with some coax in between).  How does that affect the radiation efficiency/?
> On Thursday, July 3, 2025 at 01:57:33 PM MST, Jim Brown <jim at audiosystemsgroup.com> wrote:
>> https://www.dxengineering.com/parts/cha-ss25
> That looks like a great solution, Dave! I strongly suggest against a
> loading coil for 40M, using a tuner built into the radio instead, with
> or without some top loading. Loss in short lengths of decent-size coax
> on 40M is pretty low, even with significant mismatch. An excellent study
> in QEX about ten years ago showed that inductive loading at the base
> greatly reduces the radiation efficiency, because it's at the current
> maxima! The study included the construction of multiple configurations
> of loading, and very rigorous measurements.
>
> 73, Jim K9YC
>
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