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Author Topic: EH antennas  (Read 334 times)
IZ2HDN
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Posts: 24




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« on: May 22, 2008, 05:49:04 AM »

good morning!
Does anyone have experience in using an EH antenna?
It seems to be very ...site..sensitive!
thanks
best '73 de IZ2 HDN Max
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N3OX
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Posts: 8847


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« Reply #1 on: May 22, 2008, 06:06:30 AM »

"It seems to be very ...site..sensitive! "

The antenna is one of a number of antennas that tend to excite the feedline shield much more than the antenna structure itself radiates. It probably works best when placed at the top of a feedline that goes straight up something around 1/4 wavelength (or perhaps a slight bit more?) that's grounded at the base to a good RF ground.  Of course, in this case it would be simpler to use a self-supporting radiator of the same height and match it at the *bottom.*  

Everything I've ever read about their "theory of operation" is total nonsense.  

It's a tank circuit feeding your feedline-antenna at its high impedance end.  You could do exactly the same thing with a conventional inductor and variable capacitor parallel resonant circuit with the bottom end of the coil connected to the coax shield, the top end of the coil connected to a 1 or 2 foot whip antenna, and the center conductor tapped on the coil for a good match at resonance.

73,
Dan



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73,
Dan
http://www.n3ox.net

Monkey/silicon cyborg, beeping at rocks since 1995.
WA3SKN
Member

Posts: 5493




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« Reply #2 on: May 22, 2008, 06:56:42 AM »

The antenna appears to be "two capacity hats and a coil" design.  This will have a high "Q"... fine for "single channel/frequency" assignments but not very useful for ham use.  As a "tank circuit" it would be highly affected by it's surroundings.
The "Laws of Physics" haven't changed!
73s.

-Mike.
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IZ2HDN
Member

Posts: 24




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« Reply #3 on: May 22, 2008, 06:58:38 AM »

Thanks for the infos Dan.
I was also questioning about thinghs put aside the antenna(i.e. other support pipes,vertical antennas and so on)and how they can decrease the EH antenna efficency.
best '73 de IZ2 HDN Max
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N2FQ
Member

Posts: 13




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« Reply #4 on: May 22, 2008, 08:46:54 AM »

I wanted to send this to your email address but your call
not found in QRZ.COM.

So here are some links for you to browse and you

contact these builders.

<http://www.darc.de/f39/bastel/2003/berichte/2003.html>

<http://www.darc.de/f39/bastel/2003/wb5cxc/1.htm>

<http://f5swn.2.free.fr/index.php?lng=en>

<http://f5swn.2.free.fr/articles.php?lng=fr&pg=12>

<http://www.xs4all.nl/~pa0fri/Ant/Isotron/Isotronant.htm>

<http://www.qsl.net/iz7ath/web/home_eng.htm>

enjoy
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W3JJH
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Posts: 1421


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« Reply #5 on: May 22, 2008, 09:04:59 AM »

When any radiator (antennas for RF, loudspeakers for sound, etc.) is very small compared to a wavelength, it will always have the following two properties:

1.  It will be an omnidirectional radiator.

2.  Its radiation resistance will be poorly matched to the characteristic impedance of the medium, so it will be very inefficient.

"Ye cannae change the laws of Physics!"--Lt. Cmdr. Montgomery Scott
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W8JI
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Posts: 9296


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« Reply #6 on: May 22, 2008, 03:11:48 PM »

The antenna is a cruel hoax.

See:

http://www.w8ji.com/e-h_antenna.htm
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