I modeled a Beverage 250 ft long and six feet high. Using four loads
spaced 20,40,60 and 80 percent, optimum pattern occurred with
with 400 ohm reactance series connected inductors and 900 ohms
termination.
If you double the loads the reactance for each will be 200 ohms.
It may be optimized further from this value, but the phase looked
right (180 degrees shift in every 1/4 wl of length) so it is probably
close to optimal.
Back in the slinky threads, I tried to point out there is one optimum
inductance per unit length for a slinky. It has nothing to do with the
amount of wire in the coils except as that might change reactance
per unit length. If reactance is too high, the antenna tries to fire in
the reverse direction (null at termination end and response towards
feedpoint). If reactance is too low, it doesn't have the best pattern
you could obtain for a wire that spatial length.
We sometimes have the misplaced notion that the length of wire in
small helically loaded antennas is what sets the electrical length,
but that isn't true. It is really the distributed inductance and
capacitance. Results are the same no matter how you load the
antenna as long as phase shift is about 180 degrees per 1/4 wl in a
half wave antenna.
A string of beads, a string of lumped inductors, or a continuous
helical (slinky) would all work the same. They are single band
antennas when optimized. These will not be broadband antennas,
because they depend on phase shift to "act longer" and the
reactance will double with double frequency when you really need it
to decrease dramatically as frequency increases!
73, Tom W8JI
w8ji@contesting.com
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