In , Lancer
wrote:

snip
The current distribution for the coil isn't uniform,
(input current output current). So it won't evenly dissipate heat,
it will be hotter where the greatest current flow is.

Good point.

snip
..... In fact, coils with very high Q are very poor radiators.

No, but an antenna with a high Q coil is more efficient, due to the
lower loss in the coil.

I think that was intended to mean, "....an antenna with a high Q coil is more
efficient than an antenna with a low Q coil,....", which isn't exactly true.
There are many helical antennas in use. As inductors they have very low Q, yet
they are more efficient radiators than some antennas with high Q loading coils,
and far more efficient radiators than the coils themselves. Don't forget that
resistive loss is -only one- of the factors that determine radiation resistance.
Again I point out that those huge loading coils have significant eddy current
and reflective losses due to the fact that they are so large and are mounted
with the axis perpendicular to the roof of the vehicle. And if that roof is
ferrous (as most of them are), that's just like adding a solid iron core to an
HF air-core coil -- bad news. Although increasing the conductor diameter (and
therefore the overall size of the coil) is a basic technique to achieve a higher
Q, it is nonetheless 'basic' and fails to account for all other relevant factors
in the intended application, even factors that can negate any improvement that
would be expected from the bigger coil.

Besides that, they are ugly. But if someone want's to drive a vehicle that looks
like it collided with George Jetson's space buggy then that's their problem, not
mine.






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