At 11:14 AM 2007-02-12, Gary, K9RX, StellarCAT wrote:
>I was wondering - is there anything that prevents one from
>designing an antenna for 80 with hi-Q coils such that the
>resonant frequency is around 3.52 - 4% (to be used as a
>reflector at the low end)... and then have a shunt capacitor (if
>needed vacuum variable) at the feed point to "tune" it up the
>band to as high as 3.9 + 4% (to be used as a director at the top
>end)? Obviously the Q of the cap is very high and it should (?)
>be able to handle the high currents I would think...
>
>The idea is to have 2 elements with motor driven caps -
>basically a "steppir" for 80 that would follow one around AND
>allow "instant" direction change.
>
>Will EZNEC model this very well (the lower cost $80 version)? It
>would consist of both lumped inductance as well capacitance.
What you are suggesting seems quite feasible, but you will probably
have to place the capacitor in series with the feedpoint (and the
series inductance) to achieve your goal. Of course, you may also
need some sort of impedance matching, such as a hairpin (my
favorite), to match the feedpoint to 50 ohms. This could be done in
either a horizontal or vertical (worked against ground) configuration.
Not only will the $80 version of EZNEC model this array, but even the
free version of EZNEC (limited to 20 segments) will work well unless
the elements exceed 1/2 wl long.
If you have an idea of the configuration and dimensions you are
considering, I can create a model that you can load into EZNEC to get started.
73, Terry N6RY
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