[Lowfer] Antenna questions

[Stewart Nelson]

Hi all,

First, many thanks to Lyle K0LR for the analysis, antenna models,
and pointers to software.  Also thanks to Dave WX7G, Paul W0RW and
Mike KB6WFC for the additional comments and links.

As a result, for both legal and mechanical reasons, I will attempt
something less aggressive: a  mast with a skeleton top hat.  I have
a few questions not answered by the models.

First, how are these top hats constructed?  Are they supported just
by the top of the mast?  What material is used, and what are practical
size limits?

Since the hat is likely to be quite heavy, thereby requiring a stronger
mast or better guying, perhaps most of the loading inductance should be
put up there, too.  But this is hard to analyze, because more inductance
is needed if it's up top, and assuming constant Q, this means more series
resistance, wiping out some of the improvement.  If an upstairs coil needs
to be made smaller and lighter, the lower Q might wipe out the remaining
(modeled) improvement.  But the model doesn't include the reduction in
effective ground resistance which would result from not having high
voltage on the mast.  How significant is that?  Does anyone have experience
with top loading?

Finally, my mind boggles at the thought of putting more than two miles of
wire into the ground.  I had not realized that TEXAS and OK had put so much
effort into their antennas!  Is the there any way to estimate how much more
ground resistance would result from using "only" 60 radials, or making them
50 feet long?  I know that this could be measured experimentally once I get
the mast up, but I don't want to put a lot of effort into a fancy coil, if
most of the resistance will be in the ground system.

73,

Stewart KK7KA