Buck wrote:
I have aluminum poles of three diameters, 1.5, 1, and .5 inches. I
have enough of the first two to create a pole of about 15 feet each
and about 8 to 9 feet with the 1/5 inch poles. The poles are no more
than 4 feet long each, but they are able to tuck inside each other,
at
least for the same diameter.

What I want to do is to make up a 'kit' with these that I can take to
the field to setup whatever antenna I want to use at the time. For
example, I might set it up as a 20 meter vertical in one
configuration, but in the evening, I might reconfigure it to 75
meters
or 15, or 30 or whatever I desire.

One consideration is to create a high-q coil for it. I am thinking
of
using 1/4 inch copper tubing to make a ten to twelve inch diameter
coil so I can match it to the lower bands.

That thickness of coil is overkill....

I have been reading that
base loaded coils have to be matched to the antenna, but center
loaded
verticals are more closely matched to 50 ohms.

The loading coil is used to tune out the capacitive reactance.
The input impedance will vary to length of the vertical, coil loss,
ground loss, etc..Just because a center load is used, doesn't always
mean the input impedance will end up 50 ohms..

from what I have been
reading, the center loaded coil requires more turns and a top loaded
coil even more.

Yes.

A capacity hat is also a viable option.

It's the best option. And top loading is best using capacitive
loading, where as if using a coil for top loading, the coil losses
overshadow any increase in efficiency from the improved current
distribution, etc.. Top loading using wires is the best system you
could use, if you can swing it.

I am wondering how much I am helping or hurting myself with the
larger
coil or if I would be better off with a smaller coil.

It's not that critical...

One thought is
to connect x number of poles, then the coil, then another set of
poles
or a whip to make the final adjustment for the match or to match the
antenna by tapping the coil.

I am open to all suggestions, but I am interested in knowing the best
location for the coil and the best size for it.

The *best* location for a loading coil is appx 2/3 to 3/4 up the
radiator. But even half way up is fine. Base loading is the least
efficient, and has the worst current distribution. But it uses the
least number of coil turns, and would have the least coil loss.
Being low, it's the easiest to adjust also...
Don't forget that the ground system for a short loaded vertical,
becomes even more critical than for a full 1/4 wave vertical.
It's for this reason that I usually avoid verticals for portable
use, unless the ground issue can be dealt with. IE: at the beach
is a good place for verticals...But in the boonies, on lossy, rocky,
ground, they may not do so hot if you have no radials. In that
case, I would take the vertical "sticks", and hang a dipole from
them...:/ My mobile antenna is my usual "portable vertical"...MK