[Elecraft] EFHW

[Fred Jensen]

I suspect you're going to get a lot of opinions on your question 
[end-fed half waves], and a lot more on subjects well removed from your 
questions ... such is the behavior of lists. [:-)

Any half-wave wire fed at the end will present a very high impedance 
[multiple K-ohms] and will require some transformation to a value that 
the Elecraft ATU can handle.  Transformers in the 9:1 [turns ratio] 
range will take 4K down to 50 ohms.  For QRP [i.e. SOTA], they're 
commonly autotransformers wound on small, light ferrite toroids.  The 
high current portion [where most of the radiation occurs] is in the 
center, and a single pole will get it elevated and the antenna can serve 
as two guys for it.  There is little electrical value in elevating 
either end although often, hanging it from a tall tree is physically 
easiest.  A half-wave wire is a resonant dipole and radiates like any 
other resonant dipole ... more or less broadside like a donut with the 
wire through the center.  They are quite popular with the North American 
SOTA folk.

I use a 41.5 meter wire on our wood fence here at home.  It works 
surprisingly well, and is invisible to the HOA.  I run 100 watts, I 
decided more might cause problems with the neighbors and I've sold the 
KPA500 and KAT500.  It is NVIS on lower bands [only 2 meters high], and 
the pattern is somewhat complex on the higher bands but I make a lot of 
Q's with it on CW.  I too use an Alexloop in the field.

Possibly the biggest advantage to an EFHW is that there's usually no 
transmission line involved for field operation and they're thus very 
light and stow compactly.  There is an NA-SOTA Yahoo group you might 
join, lots of discussion about field antennas.

73,

Fred ["Skip"] K6DGW
Sparks NV DM09dn
Washoe County

On 2/8/2017 2:41 PM, Dan Presley wrote:
> Wanted to get some thoughts from folks about pros and cons of an end fed half wave for portable/SOTA use, as opposed to just using a random length wire with a counterpoise connected directly to either the KX2 or 3.(I think Eric recommended somewhere around 28’ depending on the band coverage).Is there any particular gain advantage? To me the only obvious advantage is not having to deploy a counterpoise-with the end fed usually the length of coax will act for this, and of course the need for a suitable Un-Un,usually 9:1. My preferred antennas these days are lightweight resonant dipoles, which is fine assuming you have room to erect them, and second is a magnetic loop which I’ve had good luck with. I use the Alexloop-very light and easy to set up;ground and height independent generally. But-since you never quite know what will work best I try to be ready for whatever comes up. I have a variety of lightweight poles to use with wires.  I’ve had pretty good luck with throwing a random length in a tree or pole with a counterpoise, usually elevated if possible.The auto tuners in the elecraft rigs are excellent in my book. I think over the years I’ve used a bunch of portable antennas except the EFHW-just curious what the advantages might be.
>
> Dan Presley  N7CQR
> n7cqr at arrl.net
>
>
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