> If I recall correctly, the feedlines must be open-circuit (OC)
> because ~3/8 wavelength OC adds inductance to make the undriven elements
> look like parasitic reflectors in the system. I guess they could be
> made ~5/8 wavelengths and shorted if you didn't mind the cost of another
> 1.25 Vf wavelengths of coax (5 X .25 wavelengths X Vf).
> 73, Bill W4ZV
I didn't actually calculate it, but in open or shorted lines (stubs) used as
inductances or capacitors there are extra losses that finally decrease the
circulating current in the parasitic element, expecially if the line is a
low impedance coax.
This loss is not so evident on 160m but exists and is surely bigger in
coaxial cables than with open wire lines, increasing quite rapidly with
frequency.
For maximizing gain and directivity it's convenient to reradiate all the
energy from a parasitic element and so it's better to design an added
reactance of this kind taking care to use the shortest lenght of cable that
produces the desired inductance or capacitance.
73,
Mauri I4JMY
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