Hello Lech and all.
On a commercial transmitting site there are reasons for caging the loading
coil but it does not include enhanching the rf intensitity of the radiated
signal, in fact the opposite.
The commercial operators place the coil at a convenient place for tuning,
then have to cage it to protect staff working in the vicinity.
They have other consideration depending on the tx site like weather
variations causing detuning and they go for stability and sacrifice some
efficiency. These factors do not normally concern the radio amateur on LF
because of the low power involved.
The antenna loading coil is an integeral part of the actual antenna system
and needs to be placed UNCAGED under the antenna vertical for maximum
efficiency.
As I said before the loading coil unshielded at the base of a short vertical
also contributes to the radiating efficiency, and if you can manage a part
helical wound vertical that is even better. Any deviation from this method
only degrades the antenna system, regardless of what Marconi, Decca or
Polmvhetztc said.
G3KEV
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