Ron Rosson wrote:
> I wish to put up a 2 top-loaded vertical for 160m (1.83 MHz.)in a
> phase array.
>> I can go 80 feet up and the top-loading "T" wire can be up to 80 feet
>> if need be
>> I'd be grateful for suggested values and modeling for a phase array
>> and measurments for 14ga stranded copper wire.
> Seem I'm new and learning modeling of Wire antennas.
> Thanks in advance
>
> 73 Ron N6XT
I have actually built an array like that, 90 ft with four 30
foot top loading wires sloping down about 45 degrees. Two
key points. 1. Carefully trim each antenna to 1.83 MHz
resonance by tweaking the top wire or using a series reactance
at the base. 2. Use a driven feed system following the Llewellen
method. Parasitic feed will be VERY narrow bandwidth. In a pinch,
you can simply tune the phasing network for best front to back
ratio, but it is better to be able to measure the currents and
set for equal currents at the correct phase, which should be
180 degrees minus the degrees of spacing of the antenna. E.G.,
1/8 wave spacing is 45 degrees and phasing should be 135 degrees.
For optimum bandwidth, put a phase inverting transformer at
one of the antennas, so the phasing network only has to realize
45 degrees of phase, not 135 degrees. To get more bandwidth,
put switchable reactances at the bases of the antennas. The
phasing network itself is fairly broadband and shouldn't need
to be retuned after QSY. This is a fairly advanced project and
maybe you should learn about modeling with something simpler
first. Get a copy of "Low Band DX'ing" of course.
Rick N6RK
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