Re: NEC-LIST: Negative driving point impedances in phased arrays

> -----Original Message-----
> From: nec-list-bounces+p.s.excell=bradford.ac.uk_at_robomod.net
> [mailto:nec-list-bounces+p.s.excell=bradford.ac.uk_at_robomod.net
> ] On Behalf Of Jim Lux
> Sent: 04 January 2005 15:20
> To: nec-list_at_robomod.net
> Subject: Re: NEC-LIST: Negative driving point impedances in
> phased arrays
>
>
> "Peter Excell" <P.S.Excell_at_Bradford.ac.uk> writes:
>
> I would expect such a situation to occur
> > routinely in most arrays, unless very widely spaced.
>
> I don't know that "routinely" is the case (in fact, that's
> what I'm trying to get a handle on). Consider that a
> Yagi-Uda has closely spaced elements, but doesn't extract
> significant power from any of the elements.

But I think that's only because all the directors are short-circuited:
if you cut them and attempted to measure the impedance I think most
(all?) of them would be -ve. I confess I'm just using intuition here,
which is very risky!

  Likewise, I
> think a broadside linear array with uniform excitation
> probably has no negative elements, even if it's scanned
> somewhat off-broadside.

OK, I'll buy that.

Peter Excell
(BTW has anyone else had trouble with what seems to be a very
disciplinarian new "you will follow best practice for postings" filter
on this site? Two of my innocuous replies were bounced at first)

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