I'd like to add, after much modeling and in-the-air measurements, that
two-element, multi-band quads have their own impedance characteristics that
are very dependant on how the various bays/bands are fed and the dimensions
of the antenna as a whole. In a yagi, the drive impedance usually falls
within a "normally expected" range. With the quad, the impedance can vary
over a 3:1 range as the various design parameters are changed. Monoband
quads are obviously more predictable. If one is starting from scratch, I'd
advise a really rigorous modeling program to acquaint one with the quad's
characteristics before starting a build.
...robert
At 01/16/2008 14:28, Joe Giacobello, K2XX wrote:
>I agree with Norm and others that the quarter wave 72 ohm matching
>sections are simple and effective for matching a typical two element
>quad. Although most of my experiences are with four element quads, it
>is likely that your six element quad has a feed impedance in the
>vicinity of 50 ohms to start with. My observation has been that when
>going to four elements, the impedance generally drops to around 50 ohms.
>
>It would be worthwhile to model your quad in order to see just what the
>impedance is. You might be able to make some adjustments to element
>lengths, if necessary, to push it toward 50 ohms without sacrificing
>performance.
>
>73, Joe
>K2XX
>
> KZ4USA wrote:
>
> >Trying to decide which way is the best way to go with my large 6el Quad
> design.
> >
> >
> >
> >Jack
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Robert G. Strickland PhD ABPH - KE2WY
rcrgs@verizon.net.usa
Syracuse, New York USA
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