Wrong again ... the folded element transforms the ground resistance
right along with the radiation resistance.
Look at it this way. Both the radiation resistance and the ground
resistance are present in combination at the feedpoint of a normal
monopole. Folding the element merely makes an relatively efficient
transformation of what is already there at the feedpoint. The folded
element is essentially nothing other than a transmission line, and it
has no way of knowing where that which it sees at one end came from. it
doesn't distinguish between the components.
Dave AB7E
On 10/1/2013 2:48 PM, Ron D'Eau Claire wrote:
The important value is the resistance at the feed point of the radiator,
independent of any matching devices used.
Adding a 4:1 or other transformer is simply adjusting the impedance the feed
line sees, like any other matching network you might use. It has no effect
on the feed point resistance of the antenna.
A 1/4 wave long folded radiator has a feed point resistance of 4x the
typical 1/4 wavelength radiator, quite independent of the ground system.
Hence the efficiency is higher.
73, Ron AC7AC
-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of Roger D Johnson
Sent: Tuesday, October 01, 2013 12:41 PM
To: [email protected]
Subject: Re: [Elecraft] Random wires
This is NOT true! It merely raises the feedpoint impedance...just the same
as adding a
4-1 transformer.
73, Roger
On 10/1/2013 3:10 PM, Barry LaZar wrote:
As I read your post, I infer that at the moment you are wanting to
add 160 meters to your capability. An antenna that I have used and
liked is the Twin Lead Marconi. It's a simple, cheap, and effective
antenna. I first saw it written up by Bill Orr years ago. The premise
of the design is that a quarter wave antenna driven against ground may
not be the most efficient antenna due to low radiation resistance.
Therefore, raise the radiation resistance by using the theory of a
folded dipole. The folded element raises the radiation resistance by a
factor of 4 for 2 elements as the impedance changes as the square of
the number of elements. You will still need radials, but your ground
losses will decrease.
73,
Barry
K3NDM
--
Remember the Liberty (AGTR-5)
http://www.usslibertyveterans.org/
http://www.gtr5.com/
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