[TowerTalk] EZNEC question

[Mike Walker]

Dave 

We modelled this with AO and put it into play for CQWW SSB 97.  Worked great.

Ken VA3SK, did some of the work on this, and he will likely respond to this
as well.

Here is a quote we just sent to someone else:

Gary
Mike asked me to respond since I do most of our antennas work at the contest
station.
I'm not sure that using four sources is really a valid way to model the
slopers if you are going to only excite one in real life and have the others
as parasitics. What I did to model the system here was to put a lumped
inductive reactance at the feed point of the parasitics which equals the
inductance that the 150 degrees of open ended coax attached at these points
would present. I'm not sure if eznec will allow for this since I've never
used it, but I'd think that it is possible. The original article on the
antennas used all driven elements, and then Tim K3LR took it one step
further and made parasitics rather than active elements out of three of the
elements.
One thing that I have thought about but haven't tried is exciting two
elements and making the two rear ones parasitics. Might be worth trying.
The reason that K3LR went the route of parasitics was the dificulty in
getting the currents correct in each element.

I hope that this helps Gary, and feal free to ask more.

regards...mike  VA3MW

At 03:54 PM 10/12/97 -0500, David Clemons wrote:
>Hi,
>
>        I am trying to model a 4-wire lazy-V array on EZNEC.  The array
>(as designed by K3LR and others in August 1994 QST) uses RG8X feedlines
>which are 153.45 degrees electrical length.  One feedline is chosen at
>the switchbox, and both the centers and shields of the others are totally
>disconnected from each other and ground.  Thus the feedline lengths
>together with the wires act as a reflector.
>
>        According to the EZNEC manual (page 58, "Phased Arrays"): "EZNEC
>allows you to model phased array feed systems provided that they are made
>exclusively of transmission lines, and provided that the transmission
>lines don't interact with the antenna as wires."
>
>        It appears to me that this prevents me from modeling the system
>as it really operates, however, I am impressed enough with the EZNEC
>software to think that there must be a way to do it.  Am I misunderstanding
>something here, or is there a way to work around this issue?  Any ideas
>from users of EZNEC who have done this would certainly be appreciated.
>
>73, Dave Clemons K1VUT
>
>
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=================================================
Mike Walker VA3MW
Corbeil Contest Club

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