For a fan dipole there is much coupling between the two wires, so making
them different lengths doesn't really buy much in bandwidth. If you take
one of the wires of your fan dipole and put it at right angles to the
other, ending up with "X" crossed dipoles, you can make the two dipoles
act like separate antennas. You can then get a double dip SWR curve. If
you make one resonate on the low end of the band and the other at the
high end of the band, you can cover the whole 80 meter band with
reasonable SWR. This antenna is a cloud burner, not a DX antenna. It is
more omnidirectional than a dipole, and slightly less gain compared to
the broadside direction of a dipole.
Michael Tope wrote:
>I tried modeling that with EZNEC and it didn't seem to help much,
>so I ended up keeping the lengths the same. I also modeled the two
>wire bow-tie dipole with the open ends and with the ends closed
>(as with Tom's cross spreader). Aside from changing the electrical
>length, adding the spreader wire didn't seem to improve the bandwidth
>noticeably. For the 80 meter version that I installed at the local club
>station (inverted-vee configuration), the modeled VSWR bandwidth
>was in good agreement with the measured VSWR bandwidth, so
>I trust the model at least a little.
>73 de Mike, W4EF.........................................
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
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