[Elecraft] EH antenna??

[Trevor Day]

I took an interest in 'EH' antennas around a year ago and I am still not 
convinced either way.  I will say however that there are aspects of the 
EH performance that I find it difficult to explain.  In brief:

With the exception of 6m, the antennas below are driven by my K2 at 
around 10 watts with a fixed length coax feeder of four feet.  Each 
antenna stands on the window sill inside the shack directly in front of 
and slightly above the radio.  The shack is in a spare room around 12 
feet above ground in an urban environment.The 6m antenna has a 
transverter in circuit but otherwise the same conditions apply.

The first antenna I built was the simple 20m version on a cardboard tube 
(This is the 'taster' antenna you can construct in 30 mins on the 
kitchen table).  It is about a foot long or thereabouts and I did get it 
to resonate but the performance was fairly poor.  A few CW QSOs into 
central Eu with reports around 449 were about the best I could manage. 
I only spent a day with this one and the band condx *could* have been 
poor.  (I do not have any HF antennas at this location normally except 
for a random wire).

The next was a simple version of the 40m antenna.  This weighs in at 
around 4 inches in diameter and about 2 feet long.  It performed 
reasonably well, with QSOs around the UK and into central Eu on CW and 
SSB.  I was encouraged enough to build a second version, this time with 
the more complex matching arrangement.  This worked as well as the first 
(direct comparisons were not possible, so any small improvement was 
likely to go unnoticed).  I did manage to receive a 559 from a W2 before 
being flattened by QRM!
   The most significant thing about this antenna, and the factor that 
makes it so obviously different from an ATU loaded chunk of metal, is 
its bandwidth.  Once tuned (I use an MFJ Analyser) its bandwidth on 40m 
between the 2:1 SWR points is in excess of 100 kHz.  Try and achieve 
that with a commercial mobile whip, never mind less than 2 feet of metal 
tubing.  If anyone can explain it within conventional antenna theory 
then I would be pleased to hear it.

Out of interest, and largely as a novelty, I built a 6m version.  It is 
0.75 inch in diameter and around four inches long. It is wound onto 
polythene tubing with a BNC socket at the bottom to connect the 4 foot 
of feeder.  It is too small to stand on its own, so it hangs by a few 
inches of nylon cord from the curtain rail.  During last summers SpE 
openings and with 4 watts (the max my barefoot transverter will supply) 
it worked all over Eu mainly SSB with S9 plus reports in most cases.  I 
managed one comparison with my outdoor 5 element yagi on a 'real' dx 
signal from the Caribbean; with the Yagi 559, with the 'EH' 529.  Not 
bad when you consider the Yagi is 10 feet above my roof and the EH is 
indoors, 20 feet lower, and in a window facing East (the opposite 
direction)!

My apologies for the lengthy response, but I see many postings about 
this antenna from people who have read the alleged theory and come to 
their own conclusions but have never tried it for themselves.  I have to 
say, that I have difficulty with the explanations of how this antenna 
works, but I am more interested in results rather than the theory.  I am 
sure that there is probably a set of circumstances that will explain all 
of the above results; but will someone please explain how this antenna 
achieves the bandwidth that it does without being a dummy load?  (It 
doesn't get warm and it does radiate)

Trev G3ZYY



In message <000001c2daf2$4e2ce0e0$6401a8c0@easystreet.com>, Ron D'Eau 
Claire <rondec@easystreet.com> writes
>Thanks. A couple of people pointed that an "EH" antenna is "small". From
>the reference document that I read, I saw NOTHING about it being
>especially small.


-- 
Trevor Day