Swiss helical Antenna for 136 KHz
Fri, 02 Jan 1998 17:43:12 -0500
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The attached file was supplied by Sergei Ludanov KD6CJI, and
is a description of the antenna built by Toni Baertschi
These helical antennas can be calculated (up to a point)
with a program named "helical3.exe" available on
Happy New Year and 73
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From: "Ludanov, Sergei" <FISLUDAN@DOF.CA.gov>
To: "'Andre Kesteloot'" <firstname.lastname@example.org>
Subject: RE: Helical?
Date: Fri, 2 Jan 1998 11:15:17 -0800
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>Do you know this fellow? details of his antenna?
I have some info:
Not too much, but might be of interest for you.
73s and happy New Year!
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The antenna I built is wound on plastic irrigation pipe which is very
cheap. You can purchase it in different lenghts and diameters and they
can easely put together. I bought them in pieces of 2m with a diameter
of abt. 4 inches, but for the moment I use them only for the lower part
(8m) of the antenna. the upper part is helical wound on a keflar (or
fiberglass) fishing pole. But I have the intention to use the irrigation
pipe for the whole vertical part of 15m in the future. The only problem
is, that the "thing" gets heavy and difficult to handle.
Of course you should use the thickest possible wire to minimize
resistive loss in the antenna.
As a rule of thumb you need to wind a half wavelenght of wire on the
helical to get resonance. So for 190kHz would be almost 800m (abt. 2400
feet). But you should take the top load into consideration. I did not
wind so much wire on the antenna - only abt 400m because of my heavy top
load (55m horizontal wire), and I still had to add a base coil (in my
case abt 1mH) wound on a plastic paper bin. This allowed me to match the
impedance of the coax-line to the antenna by taping this coil.
To keep a distance between the single windings is difficult, so I
decided to wind the helical in tight packets of 5 spires and then leave
a distance to the next package (abt an inch or so).