On Tue, 9 Feb 2010 15:33:57 -0000, "Barett"
wrote:

Also how much impedance could I expect to gain every time I added another
FT140-43 ferrite onto the stack?

Hi OM,

Z varies by the square of turns THROUGH the center (turns are always
integers, not fractions). Z is a function of formulation (the mix of
the ferrite) which defines the optimum band(s) of operation. Z is
also a function of mass, but it doesn't take much, a small bead that
comfortably girdles RG58 will present several 10s of Ohms Z. Z is a
function of frequency, but most ferrites exhibit very mild shifts in Z
as frequency changes. You can chain beads or toroids to build up your
Z. You typically want your choke at least 3X the Z of the feedpoint -
10X is very much more preferred.

As for resources and cost, go to your nearest computer monitor
recycler and obtain any deflection coils that may still be around in
this era of flat screens. They have been reportedly quite useful.

If you do this, you will have to characterize the formulation of the
available ferrite through experimentation. If you have an antenna
computerized analyzer, you can measure this directly. If not, this
may take invention and thought (and more posts here).

73's
Richard Clark, KB7QHC