[Towertalk] Gain wire antennas for 40M
Sun, 07 Jul 2002 12:53:45 -0400
For us tribander at 50 feet folks:
I would like to put up a unidirectional, horizontally polarized gain
antenna to cover the US from here in W3 land. I had decided to build a two
element array with both elements driven because of the greater gain. I
would prefer an array that can be suspended from a single rope. There are
examples in the literature of a two element delta array with the second
element driven by a 1/4 wavelength of ladder line. One advantage of the
ladder line is that the velocity factor of 0.95 allows physical spacing
close to 0.25 wavelength.
But I am really confused about some elementary physics. Won't the ladder
line act exactly as a quarter wavelength transformer and step up the second
loop's impedance of about 100 ohms to something like 2000 ohms? Won't the
resulting currents in the two elements be profoundly different? Would the
array work well enough to fool with? Should I forget all of this and just
put up a parasitic array with the lower gain?
Sorry I need to ask such a dumb question. But there may be someone else
that is confused by such matters as well.