[Antennaware] FW: Fwd: Modelling yagi split DE

[Charlie Ocker via Antennaware]

Hi Joe -

Thank you for the tips!  I was mainly trying to use EZNEC to validate 
the YO generated design.  YO has the ability to account for balun leads 
- both length and wire size - as well as the spacing between the DE.  It 
seemed logical to me to model the DE "split" with a wire, and apply the 
EZNEC source to the center of it.  This method does not work.

I've learned that you need to keep something adjustable on homebrew 
yagi's that started life as a computer model.  I plan to leave the DE 
tips adjustable and have a couple of iterations of taking the yagi up 
30' or so on the tram and back down again for tweaking.

73,
Charlie  N9CO

On 7/9/2014 10:39 PM, Joe Subich, W4TV wrote:
>
> Charlie,
>
> If you're concerned about the balun leads, it's probably better to
> model them as a short (4 to 6" long) section of ~400 Ohm transmission
> line.  I do not remember if YO will handle a transmission line but you
> can always take the YO design and move it to EZNEC or 4NEC for final
> tweaking.
>
> In practice if you can keep the balun leads to 3 or 4 inches, at most
> you may need to shorten the DE by a couple inches to put the minimum
> SWR where you want it.  However, with an OWA type design it's probably
> broad enough that you will never notice.  Pattern/gain are nearly
> independent of DE length - the only thing it effects is resonant/match
> point.
>
> 73,
>
>     ... Joe, W4TV