On 5/13/10 14:18 , Mark S. Holden wrote:
D. Peter Maus wrote:
On 5/13/10 13:39 , Mark S. Holden wrote:


And to include some closer to on topic content - has anyone here
experimented with using a slinky as a loading coil for a "portable"
vertical antenna? If so, any thoughts on if it's worthwhile?


That was discussed pretty much to death about a decade ago. And a
dozen or so members tried it. With, as you'd expect, mixed results.

As a quick-deploy horizontal, a slinky does pretty well in the field.
As a loading coil for a vertical, not so much. Largely because it
needs a form to keep the coil stable.



I was thinking I could put it over a section of pvc pipe.

Or I may just buy a screwdriver antenna. Can't count on having trees to
hang an antenna at a star party.

My AT-271 worked fine for RX, but now I'm doing the tx thing too.

Depending on power applied, within the slinky, you may have to
deal with volume of dissipation in the coil. It's not a copper
conductor. Nor is it uniformly round, which will make the areas of
electric and magnetic field density vary around the surface of the
conductor. And being a flat conductor will produce less effective
skin conductivity surface than the equivalent cylindrical surface
area. This will make capacitance distributed across the breadth of
the coil a more significant issue, and, dependent on frequency, this
could be a considerable tuning issue and SWL issue for the
transmitter. An antenna tuner will help with the match, but losses
in the antenna will continue to be losses, antenna tuner or not.

If losses are not a significant issue in your setup, then a
slinky can be an adequate loading device. If losses will matter,
then there are better solutions.