[Lf] [Fwd: LF: Loading coils.]

[Andre' Kesteloot]

vernall wrote:

> Dave wrote:
> >
> > Dear all.
> >
> > It was a sunny afternoon ( honestly! ) so I thought I would compare a few
> > loading coils on 136. Theory states that most losses are in the earth system
> > and losses in the coil would have to be pretty big to make a difference.
> >
> > I tried three coils:
> > My usual coil    380mm dia    500mm high    4mm o.d. wire
> > My /P coil        200mm dia    210mm high    1.25mm o.d. wire
> > Ex Decca        810mm dia    210mm high    4mm o.d. litz wire
> >
> > Guess what?
> > No difference at all!
> > At the test power, about 800W, I got exactly the same aerial current in each
> > case.
> >
> > So there.....
> >
> > 73. Dave G3YXM.
>
> This is a fairly convincing result that you have high ground loss, that
> swamps observation of the differences in coil loss.
>
> Coil loss could be assessed by separately checking them, resonated with
> polystyrene capacitors roughly equal to your top loading capacitance,
> and observing the 3 dB bandwidth.  The dynamic resistance can then be
> calculated.
>
> However, working on lowering the ground loss(es) would seem to be a more
> rewarding pursuit.
>
> 73, Bob ZL2CA