[Elecraft] PAR/LNR EFHW antenna

[Bill Johnson]

I agree with what has Scott has written.  EFHW from what I have read and experienced, generally have ~ 3000+ ohm impedance at feed point.  Thus the need for an adequate transformer, most usually to match 50 Ohms.  I use one on 160 and 80 meters (where it is really a full wave) at home by using a toroid and windings with a tap.   I do use a tuner for slight changes when the length doesn't match the frequency I choose to use.  A counter balance removes the idea and radiation of the EFHW.  A very short ground is important to remove static potential on the low side of the coil to protect equipment.  If you google EFHW's you will finds loads of great stuff to read and help you.  Good luck.  

I happen to like the ones I am using, but did buy a factory built coil after I found my personally built could not give a native match at the desired freq as my toroid did not have adequate specs despite what I had calculated would work.  The site I got my initial info from was incorrect and the co I bought the toroid and wire from had an inadequate description.  Live and learn.  My home made works best on EFHW above 40 meters.  

My commercially built transformer in the 160 has very narrow bandwidth.  A remotely operated tuner broadens it but efficiency is  reduced once off the designed frequency. In the design is the selection of wire length and height into the matching transformer.  I do have the multiband EFHW but that requires the appropriate wire length on each band.  I carry the appropriate wires in my antenna kit inside the KX2 large case.   The small gauge silk-like wire is also light and small.  I have a super light 43' collapsible shore fishing pole to string out the wire, versus getting a launched wire stuck in a tree and then be potentially guilty of littering in the state park where I like to hang out.

73,
Bill
K9YEQ

-----Original Message-----
From: elecraft-bounces at mailman.qth.net [mailto:elecraft-bounces at mailman.qth.net] On Behalf Of K9MA
Sent: Monday, January 8, 2018 7:39 PM
To: elecraft at mailman.qth.net
Subject: Re: [Elecraft] PAR/LNR EFHW antenna

On 1/8/2018 16:59, Rich Arland wrote:
> Failing that path, has anyone hooked an EFHW to the internal ATU with good results? I would also include a cut to frequency ground radial that I would lay out below the antenna. That would be the easiest thing and simple to employ.

That definitely will not work:  The impedance of the EFHW is much to high for any internal ATU to match.  The 64:1 balun may work, though I haven't tried one.  QRPKITS has a QRP tuner, but it works only on a single band.  Most any of the external antenna tuners will work, though they may be lossy.

The best solution, I think, is to build your own L-network tuner.  One coil, a 3-position switch, and one variable capacitor.  You don't have to get a perfect match, just within the range of the internal ATU, like 3:1.  Once you find the right coil tap positions, the internal ATU should be able to handle the small mismatch with different antenna installations, etc.

It may seem like a lot of trouble, but if you can match the EFHW, it's just about the most effective simple wire antenna you can use.

73,

Scott K9MA

--
Scott  K9MA

k9ma at sdellington.us

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