[TowerTalk] 4L Steppir 10m Mod - here is the file

[Jim Lux]

On 9/22/11 8:02 AM, Rick Stealey wrote:
>
> I got a few requests for the file.  Here it is.  This is the 3 element SteppIR with an added reflector closer to the driven element.  It would be easy to add a director similarly.  If you want to see the effect of such an element on the other bands you would take the original dimentions for the other band and stick this reflector in and see if it affects the pattern or swr.  That's what modeling is all about.
> The file is easy to use because all variables are defined.  You can change any of the SY lines to suit your own needs.
> It should not be necessary to change the GW lines.
> The values in this file were determined by using the optimizer feature in 4NEC2 to get best f/b.
> I used the latest release of 4NEC2     (5.8.7)
>
> Rick  K2XT
>


This is a great example of what modeling can do for you.  A simple 
model, you can quickly fool with it to get a semi-quantitative 
understanding of whether a change is worth trying.
>
> CM 3-element Yagi, ten meters, SteppIR elements, the 28.2 setting
> CM    'The antenna will actually appear to be higher in freq. than in reality due to loading of the elements by the fiberglass
> CM    'This is the 28.2 configuration, but designed for 28.8 MHz
> CM    'The fiberglass supports load the 28.8 lengths so they work at 28.2 MHz.   ok ?
> CM

I wonder if we could come up with a suitable LD card that represents the 
effect of the fiberglass.  I generically dislike schemes that wind up 
tuning the antenna (in the model) somewhere different, because the 
spacings really need to scale too.

Maybe a distributed L/C/R loading?  In NEC4 you might be able to get 
there with "insulated wires", but it would be nice to come up with a 
rule of thumb technique for NEC2.