Mal said...

NEVER put your loading coil in a metal box, it totally destroys the
efficiency. Consider it as part of the antenna from the radiation point of
view. You have never seen a loading coil on a Mobile encased in a metal

CAN,

the coil contributes to the over all efficiency ie coil plus whip.

I hope somebody tells the BBC and other broadcasters not to put their
loading coils in metal shielded "ATH"s because they will keep doing it! If
you think they aren't worried about efficiency, think again! Inefficiency at
QRO = heat and MONEY!!!
For what it's worth I put my coil in a metal clad shed in the garden and the
aerial current INCREASED to the effect of about 1dB improvement. The coil is
so small as to be an insignificant part of the radiating system, losses are
everything and losses due to the coil's electrostatic field coupling into
trees etc can be significant. If you coil isn't out in the clear you may
benefit from doing it but it has to be done well, dodgy joints etc will lose
you more than you gain.
As for receive noise...... have you listened on LF much?

Dave
G3YXM.