I'll confess some difficulty (probably my failing) in understanding your
point(s). To try and simplify the situation to something my pea brain may
understand, let's use a toroid at either location. Now tell me what the
difference is.
Wes N7WS
On 7/3/2025 3:39 PM, David Gilbert wrote:
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@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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