The "equal length" is one way to say "segments should align" which could
be different if the fan angles are large. Aligned segments I think is
what the math does best with. So that takes a bit of fiddling to
determine the divisor # of segments for each dipole. Of course you need
to make a good guess at the starting lengths. Close is good enough.
3 segments are not enough IMO as the currents near the feedpoint
junction are high. Another rather essential trick is to have a
transmission line between the feedpoints. My model feedpoints were
separated by 2" 50ohm lines and the ends by 20". This is discussed by
Cebik in one of his modeling tutorials. Implementation between
feedpoints was a small Cu flat strip, unknown Z, but unimportant for my
two 80/40/20 fans, especially since 20m is closest to the coax.
At least that is what I have done and gotten good correlation model to
built 3 band 80/40/20 fans.
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