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
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