[Elecraft] End Fed Half Wave

[Rick Dettinger]

I have a similar antenna.
I would use the inverted "V" or "L" configuration.  You want the center of the antenna as high as possible.
Mine is an inverted "L", but the far end actually is about 20 feet below the center, which is 50 feet high.  The maximum radiation is where the current is greatest, a quarter wave from the far end, which has no current.  Mine works quite well for a single wire.  I made it a little more than a half wave at the lowest frequency, so I can use a remote tuner at the base for other bands.  I feed it against a less than great radial system for all bands, but for a half wave, this might not be very important.  The base is 140 feet from my shack, fed with coax in a conduit.  I also have a 43 foot vertical, which I can select by remote switch.   Except on 20 M, the inverted "L" usually works better.

73,
Rick  K7MW  





On Sep 22, 2014, at 2:49 PM, <w7aqk at cox.net> wrote:

> 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
> 
> 
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