Hi All,
I'm having a disagreement about the use of this folded dipole calculator
impedance calculator.
http://www.k7mem.150m.com/Electronic...ed_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

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...ed_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



Hi,
The eq. seems right. Folded dipole is basically a loop.
Usually we use 300 Ohm feeder.
Tony
VE6CGX

Tony Hwang wrote:
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...ed_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



Hi,
The eq. seems right. Folded dipole is basically a loop.
Usually we use 300 Ohm feeder.
Tony
VE6CGX
Hi,
And you can use a tranformer 300 Ohm to 75 Ohm to use coax if need.
It becomes a from 300 Ohm balaanced to 75 Ohm unbalanced feed.

"Tony Hwang" wrote in message
...
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...ed_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



Hi,
The eq. seems right. Folded dipole is basically a loop.
Usually we use 300 Ohm feeder.
Tony
VE6CGX

In what case would I alter the 72 ohms?
Mike

"Tony Hwang" wrote in message
...
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...ed_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



Hi,
The eq. seems right. Folded dipole is basically a loop.
Usually we use 300 Ohm feeder.
Tony
VE6CGX

In what case would I alter the 72 ohms?
Mike

amdx wrote:
"Tony wrote in message
...
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...ed_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



Hi,
The eq. seems right. Folded dipole is basically a loop.
Usually we use 300 Ohm feeder.
Tony
VE6CGX

In what case would I alter the 72 ohms?
Mike



Hi,
Feed point impedance becomes near that when it is just a dipole(not
folded). On a haf wave element at center feed point the current and
voltage phase is such that the impedance is near that figure.
If it is vertical uater wave whip, the other half mirror image is
prjected into the ground forming dipole and in that case feed point
impedance at the bottom is around 50 Ohm. I am old dinosaur EE(class of
60), my brain is not as bright as it used to, LOL!

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

The way I read it is that you put in the feed impedance that a similar-
length plain-ol' dipole in the same situation would have. In a Yagi this
can be significantly lower than 72 ohms, which is the whole reason you're
considering a folded dipole.

Does the author have contact information? Perhaps you could ask the
source?

--
www.wescottdesign.com

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

Tim Wescott wrote:
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?

Hi,
Also folded dipole tends to have broader b/w compared to dipole.

Tony Hwang wrote:

Tim Wescott wrote:
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?

Hi,
Also folded dipole tends to have broader b/w compared to dipole.

Due to the transformer effect of folding it.

--
Best Regards:
Baron.