[Elecraft] PAR endz-fed

[Jim Brown]

Ron,

A few quibbles with your analysis. First, the antenna that I have described is 
a simple half wave dipole, fed at a current maxima. The only tricky part is 
the power rating of the choke that serves as the end insulator. My choke is 
NOT a matching element, it an end insulator!  

Second, this antenna interacts with surrounding objects (including the earth) 
just as any dipole would if hung in the same position, NOT as a ground mounted 
vertical would. The major loss in a ground-mounted vertical is due to 
resistive losses due to return currents flowing in the lossy earth, which can 
be made very small by adding enough radials. In MY antenna, the return 
currents are entirely within the antenna. 

On Mon, 2 Mar 2009 14:20:33 -0800, Ron D'Eau Claire wrote:

>The PAR End-Fedz (Par's spelling) is a Fuchs type antenna; an end fed 1/2
>wave radiator.  

>Its advantage over shorter radiators is that it requires very little ground,
>if any, since it's fed at a voltage loop. Efficiency is not compromised by a
>mediocre ground as is so common with radiators 1/4 wave or less in length
>because virtually no current need flow into a ground system. 

>If it's mounted vertically it will still have the induced ground losses all
>verticals have 

NO! Verticals have "ground losses" if the earth is what's carrying return 
current and terminating the field. In the antenna we're describing, the 
outside of the coax acts as the other half of the dipole, so it carries the 
return current and terminates the field!  

BUT -- for this antenna to work, the quarter-wave length of the feedline 
between the wire and the choke must be in the air (and the higher the better) 
-- that is, it is part of the antenna!  This antenna can be vertical, 
horizontal, or sloping. It can even turn corners.  If, for example, you were 
to toss it out the window of an upper floor and into a tree, it would act just 
like any other center fed dipole of the same length at the same height!  

Another point about "ground losses."  The earth serves a second function with 
any antenna -- it acts as a reflector for the field that the antenna 
generates, and the interaction of the reflected field adds (algebraically) 
with the direct field to form the antenna's vertical pattern. The BEST that 
the reflection can do is add 6 dB at low angles. If the earth is lossy, the 
reflection is weaker, which makes the lower angle parts of the pattern weaker. 

73,

Jim Brown K9YC