You're not alone Wes. I also do not understand how having an inductor at
the tuner for an electrically short antenna has a different effect from
putting the inductor at the antenna base.
John KK9A
Wes n7ws wrote:
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 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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