[Elecraft] EFHW

[Kevin - K4VD]

Brian:

The end fed I use uses a stub for 20 meters. When I set it up I tuned the
antenna for 40 meters. Then I added the stub 1/2 down the antenna and
trimmed that for best SWR on 20 meters. Worked exactly as expected with an
antenna analyzer.

K


On Sat, Feb 11, 2017 at 2:03 PM, Brian Pietrzyk <ve3bwp at gmail.com> wrote:

> This thread has really given me things to try when earth tilt/absence of
> white rain is back in our favour. Great group of folks on this forum btw.
>
> The many contributions to this thread have given me the confidence to try
> end feds (for the first time) on my up coming trip to HI9 land. I'm packing
> a few end fed lengths for whatever  the trees on the resort will support.
> I'll start with Wayne's 25ft radiator and 25 ft wire on the ground
> suggestion first. Again this untried for me.
>
> Before getting my kx3 I used an FT817 and the ATAS25. Worked fine when 20
> to 10m openings were easier to come by a few years ago. Now my thoughts are
> about the reactions I'll get throwing something at a tree or two on the
> resort near the beach. I've managed to strip my CrankIR down to 12lbs so
> I'm taking it anyway only because I've used it/know it. The goal is to no
> longer feel the need to cram it into charter flight size and weight
> constraints and keep it for car trips instead. I'm guessing throwing a half
> full water bottle will suffice. Corrections invited.
>
> Now my thoughts are about permanent end fed resonant wires (vs dipoles)
> for the home shack. I currently have a home brew 80/40 centre fed dipole
> tied from the house to a tree in the woods. If that were instead an end fed
> resonant wire fed by a 9:1 at house end things could get much simpler (and
> less saggy) coax wise.
>
> Now comes the fantasy thinking... What about making it an end fed multi
> band by either putting traps in the 80m end fed or better still adding on a
> couple of fan EFHW wires for 40 and 20? Anyone tried this? How would the
> efficiencies compare to their centre fed trap or fan dipole counterparts
> respectively?
>
> Then there is that 160m antenna I'm think about putting up this summer...
>
> Brian ve3bwp
>
> Date: Fri, 10 Feb 2017 12:05:56 -0600
> From: K9MA <k9ma at sdellington.us>
> To: elecraft at mailman.qth.net
> Subject: Re: [Elecraft] EFHW
> Message-ID: <bf058500-e443-0a91-c789-06f1abd234d0 at sdellington.us>
> Content-Type: text/plain; charset=windows-1252; format=flowed
>
> Here's the old trade-off between radiating efficiency and ease of
> matching for an end fed wire. The EFHW is more efficient, because little
> power goes into the ground system, but its high impedance is harder to
> match.  A wire of a different length may be easier to match, but more
> power goes into the ground system, where it doesn't radiate much.  Both
> will work but, I believe, on average the EFHW will be a bit better.  Is
> it worth the trouble?  Who knows?
>
> Antenna discussions have long had a tendency to focus on SWR.  Low SWR
> does not necessarily mean an antenna is effective.  There's an old
> saying, "The SWR of a dummy load is 1:1."
>
> 73,
>
> Scott  K9MA
>
> On 2/10/2017 09:56, Don Wilhelm wrote:
> > Brian,
> >
> > If your end fed antenna is actually a halfwave (which is what EFHW
> > means), the answer is no.
> >
> > The solution for portable work is to use a length that is not a
> > halfwave - 58 feet is known to work well for 40 thru 10 meters when
> > used with a 13 foot counterpoise.  Double the lengths if you want 80
> > meters.
> >
> > With that antenna and counterpoise length, dispense with the balun for
> > portable operations, and use a BNC to Binding post adapter instead (no
> > coax).
> >
> > If you need to use a short length of coax, you can put the balun at
> > the end of the coax, and you can try both the 1:1 and 4:1 positions to
> > see which provides the better match.
> >
> > 73,
> > Don W3FPR
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