[HCARC] Inverted L Antenna

[galeheise at windstream.net]

Gary-

  Short version - Efficient 1/4 wavelength 160 meter antennas based on a 
primary vertical radiation components and grounding systems in the Texas 
Hill Country are difficult to build when compared to areas elsewhere in the 
world with more conductive soils.  You might be able to build the best 
antenna in this area but compared to other areas with high conductivity 
soils, it will be poor.

  Once I built an inverted "L" when I lived in Northern Kentucky.  As I 
recall, ideally one wants the vertical component to be as high as possible 
since the current and antenna radiation at the base is at a maximum and 
reduces with length.  Bending the antenna to the horizontal simply allows 
one to obtain additional loading for resonance.  Unfortunately, the 
Efficiency of a Vertical is = Radiation Resistance of the Vertical Element/ 
(Soil Resistance + Radiation Resistance of the Vertical Element).  Since the 
resistance of the soil is so high in the Texas Hill Country the actual 
Efficiency of the Vertical is pitiful.  If one were to put out 120 - 1/4 
wavelength radials it will help the immediate area around the antenna but, 
as Dale Gaudier may have pointed out in the past, it doesn't really help in 
extended distances beyond the radials where the radiation pattern continues 
to be developed.  Also, as I recall, I was able to lengthen the antenna to 
raise the radiation resistance slightly and then had a matching network to 
the 50 ohm line.  It made it a little more efficient but not much.

  My recommendation is to research antennas for 160 meters that have a 
relatively high radiation resistance.

  I have a friend in Dallas who invented and patented a 160 meter antenna 
that requires a minimum of radials.  He took it to Los Alamos and tested it 
against a full 1/4 wavelength 160 meter antenna and obtained similar 
results.  He manufactured them, shipped them all over the world and also 
installed commercial versions for high power broadcast stations.  I don't 
recall the theory of the antenna but I suspect it may have had a higher 
radiation resistance than a regular 1/4 wave vertical such that the soil 
resistance had less of an influence.  I suspect the soil near Los Alamos is 
similar or worse than ours.

Take care,

Gale
KM4DR



-----Original Message----- 
From: Gary J - N5BAA
Sent: Saturday, February 15, 2014 8:06 PM
To: hcarc at mailman.qth.net
Subject: [HCARC] Inverted L Antenna

What happens, if anything, to an inverted L (80 or 160 meters) if the 
vertical section is right on the edge of a hill approx 50 feet up and the 
wire runs downhill to a support approx 50 feet high at the bottom of the 
hill??  Does the slope make it at all directional??

Gary J
N5BAA
HCARC Secretary 2013/14
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