[Elecraft] End Fed Half Wave

[w7aqk at cox.net]

Hi All,

Here's a question for the antenna gurus among the group.  It's about the 
best way to deploy an end fed half wave antenna.

First of all, I assume most would say to put the entire antenna up in the 
air as high as possible, and in a horizontal plane.  I understand the 
advantage of doing that.  However, what about a situation where you only 
have one support?  My first inclination would be to deploy the antenna like 
a sloper, with the far end at the top of the support, and the other end at, 
or near, the rig.  I started wondering, though, about where the maximum 
radiation occurs.  In a half wave antenna, the current max is more or less 
in the center of the antenna.  So, would it be better to get the center of 
the antenna as high as possible (taking advantage of the one support you 
might have), and then maybe bending the other half back downwards, sort of 
in inverted vee fashion?  That would be as opposed to just running the 
antenna up in a straight line to the top of the support, thus possibly only 
getting the center about half as high as the top of the support.

Here's a more definitive description of what I am thinking about, and 
compares to the situation I have.  I have a pole that goes up approx. 40 
feet.  If I deploy the EFHW in sloper fashion, with one end near the ground 
close to the rig, the center of the antenna would only be at approx. 20 
feet.  Also, On 40 meters (the band I would be using), the pole would need 
to be some 50+ feet from the rig.  Alternatively, what if I move the center 
of the antenna up closer to the top of the pole, and have the rest of the 
antenna slope back down to another tie point?  Wouldn't this be apt to work 
better, even though I have created something similar to an inverted vee?

I know a couple of RVer's who do something similar.  They have two poles in 
use, one of which is much taller.  They deploy their antenna so that the mid 
point of the antenna is near the top of the tallest pole, then over to 
another shorter pole, and then back down that 2nd pole vertically--almost a 
somewhat slanted "U" shape.  Their results seem to be decent, but I don't 
know if there is a better way to do it.  Their method condenses the lateral 
space required to deploy the antenna, thus fitting within most RV sites.  I 
don't know exactly what this does to the impedance at the feed point, but 
they use tuners to resolve any mismatch.  The pole I have is somewhat taller 
than either of the ones they use.

Anyway, I assume I could do the sloper approach without creating any serious 
issues, but I'm curious about what others think of the "vee" approach to get 
the antenna center higher.

I appreciate any suggestions.

Dave W7AQK