>
> I haven't tried a short, fat loading coil yet, but the indications are
that
> short fat coils have lower losses.
>
> 73, Dave G3WCB IO91RM
Dear Dave, LF group,
Short, fat coils wound with the same type of wire, and other losses being
negligible, do indeed have higher Q (at least, until they get really short
and fat - the optimum figure is usually given diameter = 2.5 x length;
after that Q starts to go down again). But don't get too carried away,
because the winding has to support the same voltage, and the shorter winding
will have greater voltage between adjacent turns, putting the insulation
under greater dielectric strain, which can certainly be a problem with a
high voltage antenna system.
Assuming actual breakdown does not occur, dielectric losses in the wire
insulation and the former, will increase. If the former or insulation is
made of some relatively lossy dielectric, for example PVC, it is certainly
possible to end up with a shorter, fatter coil with reduced Q - as I proved
experimentally once, much to my annoyance!
Cheers, Jim Moritz
73 de M0BMU
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