[TowerTalk] Top loading HF-6V for 160

[Dan Zimmerman N3OX]

On 10/19/07, Eric Hilding <b38 at hilding.com> wrote:
> My understanding is that use of the 160m loading coil for the HF-6V limits
> the power to 500w on 160m.
I'd believe that. The voltage across the coil will tend to be pretty fierce.

500W seems to give about 7600V across the coil. Full legal limit would be 13kV.



> Q: What if the 160m coil is left off, and 4 slolping top hat wires  were
> attached to the top of the vertical?

Commonly done and generally a decent way to top load, but in this case
it doesn't seem to work out too well.  Maybe someone else can chip in
but it seems tough to do sloping wires without cancelling a lot of
radiation and driving the radiation resistance down.  Straight out is
better.  It makes me wonder if even an inverted L with a sloping top
wire is a very good idea.  I think it might not be.

> Any idea what the length(s) would have
> to be, or would this even work?

60 feet but I don't think it works out too well if you have to slope them down.

Is it true that top loading narrows the
> bandwidth?

Generally it should widen the bandwidth over base loading, but coil
losses in the base loaded case could make the SWR bandwidth wider.

At a given efficiency, the bandwidth of a top loaded antenna will be
more than a base loaded one.

Anyway, in either case, inverted L or  top loaded with symmetrical
wires, try to get their tips as high as possible.  Too much angle and
you lose a lot of benefit of top loading, I think.

Dan