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LF: Advice on Antenna.

To: [email protected]
Subject: LF: Advice on Antenna.
From: "'Geri' Kinzel, DK8KW" <[email protected]>
Date: Tue, 14 Sep 1999 01:26:13 -0400
Reply-to: [email protected]
Sender: <[email protected]>
Hello Des,

first of all welcome to the LF group. From your writeup I can see that you
have spend a lot of time to carefully read what has been published and have
done some "training" listening into the band. This is, in my view, an
excellent approach.

I myself belong to the more unpatient people and have tried everything to
be QRV as fast as possible. This included several disappointments and a
stony road to success. If you have followed the reflector news for a while
you will see that my signal improved quite well during the past couple of
months.

I have practically experimented with a couple of antennas. If you only have
limited space available, you do not have too many options, I believe.
You have already discussed some of the options in your message and already
pointed into the right direction. To me, option 4 (vertical antenna with
3x7m top load) would be an option that comes close to what I am using.

What I finally came up with is, what in the old broadcasting literature of
the first half of this century is called an umbrella antenna. If you have
access to the internet, have a look at http://www.dk8kw.home.pages.de,
where I show my setup and a drawing of a commercial umbrella antenna from
the past.

The characteristics of that umbrella is, that the top load is not
necessarily horizontal but the top load radials can slope down at an angle
of 45 degrees or even steeper. This makes the mechanical handling of such
an antenna much easier, because you do not need supporting poles in the
same hight as your vertical mast. Those top loads should not be too long,
the geometry that I selected here is an antenna height of 18m and four top
load radials, 10m long each, 45 degrees sloping angle. To increase
capacity, I had those top load nearly twice as long before, but this setup
suffered from the fact that the top loads shielded the antenna. Shortening
those radials increased my signal (and incoming signals, or example by
DCF39) by approximately 3 dB.

My mast is made of fibreglas, and I can retract this antenna within 20
seconds down to 3m, in case of an upcoming thunderstorm, for example.

Of course, I could add the usual LF antenna advises: stay away from leaves
and trees with your radials, even at moderate power outputs you can produce
sparks that are a couple of inches long! And of course ground rods and
earth radials are essential to make the thing work. There was a previous
discussion on grounding here onthe reflector, so I am a little bit careful
just saying, the more wire you put into the ground, the better. There might
be circumstances when less is more.

Hopefully this contribution to discussion helps you to make up your mind.
See you on the band with a astrong and steady signal. Since you have build
a transverter, I am sure that you are also able to run an SSB signal, so
you are another possible station to be QRV also in more exotic modes such
as PSK31 or Hell.

Best 73

Geri, DK8KW (W1KW)




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