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[antennaware] Station Modelling

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Subject: [antennaware] Station Modelling
From: (Billy W. Cox Jr., AA4NU)
Date: Tue, 22 Dec 1998 21:06:32 -0500
Bill, W4AN brings up an excellent point !

>I received some nice mail and information from K9UWA regarding station
>modelling.  John has his entire station modelled and knows exactly what
>kind of interaction he gets from his other antennas.

Sounds like a great NCJ article to publish, or an addition to your web site

>One thing I have learned is that my 4-square which surrounds a 115' Rohn
>45 tower is definatley affected by the tower in the middle.  The F/B goes
>from a 25DB in the perfect model to 18DB or 19DB with the tower in the
>center of the square.

The tower does affect the pattern, but notice the gain stays about the same.
When you look at the F/B ... look carefully at ALL of the pattern, the 25 vs
is for ONE reference point ... not the entire back lobe ...

>Has anyone else done any complex station modelling to see the affects of
>nearby antennas?

Yes, several notes ... One is the number of "segments" or "pulses" that
the programs allow you to use. When I first started "looking for
via the PC, the early versions of software were very limiting. Second, is
no one has really published "accurate models" for the various loaded or
trapped antennas ... I normally "assume" the use of full size models is
accurate ... but is it ? Third is look closely for the interactions of your
Beverages and the array there ... After "wondering" why some of the
receive only antennas here seemed to play poorly, I "looked" at the
site via the PC ... Not only were the "too close for comfort" Beverages
not working well on receive, they were distorting the array on XMIT !
(and that's why I took the short Beverages here down ... and now
the 80m4x array receives better !)

Anything as to changes here at AA4NU goes thru the PC (EZNEC)
"in here" first before I start "out there". Taking that step has saved
me an enormous amount of time NOT putting up, or adding an
antenna that would have interacted with others and not worked well.

Ever wonder why persons "worry" about how high above the HF yagi
to put their 'shorty 40m yagi', and then hang an inverted vee 1 - 2'
beneath the main yagi, spaced only a few inches away from the
tower ... and wonder "why don't things here seem to play well" ... ?

Load up such a setup in the software and you will see ... Ditto on
why some folks have great luck with 0.25w slopers and others
setups seem to be the perfect outside dummy load ...

Bill, you are on the right track there to make your station even
better than it is today !

Happy Holidays/73

Billy AA4NU

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