On Sat, 14 Nov 2009 12:05:21 -0600, amdx wrote:

Hi All,
I'm having a disagreement about the use of this folded dipole
calculator
impedance calculator.
http://www.k7mem.150m.com/Electronic_Notebook/antennas/
folded_dipole.html
We are using it to calculate the impedance of folded dipoles to drive a
yagi.
When entering data it asks for "Simple dipole feed impedance (ohms)"
Default is 72 ohms. This assumes a 1/2 wave dipole.
The fellow I'm disagreeing with say's,
"the reason that the variable in the calculator for the "dipole feed
impedance"
could be if you want to transform the z to something else, such as 50
ohms."
I don't even understand what he means.
I can only think of one reason to alter the 72 ohms, that would be if
you use a a different length folded dipole.
I'll readily admit the other fellow knows more about this than me, but
I need more convincing :-)
Can anyone explain this to me.
Thanks, Mike

I've seen older Yagis that use folded dipoles, but the newer ones seem to
lean more toward gamma or T matches. You get more latitude for adjusting
impedance, in the gamma case you get a kinda sorta good match to coax
without a balun, and if you're employing plumber's delight construction
it's no more difficult to fabricate than a folded dipole.

So why a folded dipole, pray tell?

--
www.wescottdesign.com