I suggest reading W8JI ... and others.
http://www.w8ji.com/radiation_resistance.htm
Dave AB7E
On 10/1/2013 2:53 PM, [email protected] wrote:
Sorry roger, Roger, your analysis is not totally correct. You do raise the feed
impedence from 36 Ohms as compared to using a single 1/4 wave wire over perfect
ground. As most of us do not have perfect ground, there is an imperfect
representation of the virtual 1/4. Because it is imperfect, you can look at
this part as absorbing energy and just returning heat. By raising the radiation
impedance, less energy is absorbed by ground and more is radiated. How much
additional efficiency do you obtain is a matter of the ground system you put in
and the ground constants under it. In my experience, it is worth the effort to
build the antenna as it will outperform a similar single wire inverted L. I
suggest reading Bill Orr, and others, on this antenna.
73,
Barry
K3NDM
----- Original Message -----
From: "Roger D Johnson" <[email protected]>
To: [email protected]
Sent: Tuesday, October 1, 2013 3:40:49 PM
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
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