137 KHz Antenna

Andre Kesteloot akestelo@bellatlantic.net
Fri, 09 Jan 1998 17:40:09 -0500

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Taco Gang,

FYI, attached some additional details on the Swiss antenna


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Date: Fri, 09 Jan 1998 13:46:40 +0100
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Subject: Re: LF: [Fwd: 137kHz skeds]
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=46rom HB9ASB, JN36pt:

Radiation Resistance & Feedpoint Impedance of my helical antenna: Sorry
Andr=E9, for the moment I have no idea where I am. So far I found a lot o=
experimental work about helicals but little theory. Unfortunatly I have
no means to measure the RF current and my helical is not in resonance
itself - I have an additional loading coil at the base (abt. 1mH) which
I tap for matching the 50 Ohm Coax. I guess that the Feedpoint Impedance
is dominated by my earth losses - I connected everything to the earth I
could, including the pool (hi) but I'm restricted to a surface of 30 x
40 meters. =

To get an idea about the radiation resistance I should probably do some
field strenght measurements in the far field and compare them to
normalized curves. So I have no Idea about my ERP neither, but I'm quite
sure that I'm well below our limit of 1W ERP (TX PWR is 80W). =

I feel that a top loaded helical could be a better way to get out from a
small lot than a single wire on a loading coil, but it is very difficult
to construct and maintain. If my antenna brakes in the winter storms, I
have to wait until spring.


73 de Toni    =

Andre Kesteloot wrote:
> =

> Dear OM,
> =

> Thanks for the description of your 136 KHz antenna. What do you think i=
> 1). its approximate impedance at the feed point?
> 2) its radiation resistance?
> =

> I am considering building one similar to yours.
> =

> Thanks in advance and 73 ,
> =

> Andr=E9 Kesteloot N4ICK
> =

> Baertschi wrote:
> =

> >                                                   -------------------=
> >
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