Wednesday, August 5, 2015

Antennas for Adventure

Over the years, I have used many different kinds of antennas.  There are all kinds of theories about which antennas are the best and what should be used for different kinds of listening and amateur radio operating.  Some folks have the opportunity, space and finances to put up optimum antenna systems for what they want to do,  but most of us fall into the category of having either limited space, limited money or some kind of restrictions in the neighborhood.  So often what happens is there is sometimes a small and sometimes a big compromise on what goes up in the air.  For most of us, its a matter of what we can do and what will fit in the spaces we have.

I have been in my present home for about fifteen years.  There are lots of trees and moderate space, hemmed in by power lines, telephone and cable tv drop wires and other obstructions.  Early antennas here were suspended from tree limbs  or short masts.  The current system evolved over time and has been very successful,  though not exactly text book.

The most successful have been the variants on vertical antennas or inverted L's.  The idea being to get the lowest angle of radiation or reception possible.  Ground radials for the verticals have been made difficult by very rocky soil and tree roots close to the ground. After several years of running over radials with the lawn mower,  it was decided to attempt elevated radials or ground plane antennas.  The try, though brought about by mechanical needs, turned out to be very satisfactory, as the antennas performed very well, even with fewer radials,  even outperforming my thirty-three foot high ground mounted vertical with sixty buried radials beneath it. 

Here are the antennas that have resulted in the best DX at this location, both for amateur and SWL DX.  All are fed with either RG8X or RG8 coaxial cable.  Most are resonant on one band, but tunedto match on any frequency with either a Heathkit roller coil tuner or a Dentron Super Super tuner.  I know there are all kinds of reasons why force tuning antennas is not optimum,  but all I can say it has worked well enough for me to but 326 countries into the log.  I will leave the arguments to the theorists!
Two ground plane antennas, made from aluminum tubing and mounted atop television antenna mastswith the bases about 25 feet above the ground.  One vertical element is 21 feet high, the other is 16-1/2 feet high.  Each has four radials the same length as the antenna element which also serve as the top guy wires.  They were each gyed at the middle by plastic rope.

This is a view looking up at the mast that supports my 80 meter sloper. This is a fifty foot telescoping TV antenna mast that is not extended quite all the way with a lighter aluminum extension out the top.  The idea was to give it more strength in the middle.  It is fed at the top with RG-8X coaxial cable that can be seen coming down in the picture. The actual antenna wire is longer than would be resonant on 80 meters and was made the length that would fit sloping down to a tree at the front of the back yard.  The actual length is closer to 85 feet than the 66 feet to be resonant as a quarter wave on 80 meters.  Once again, the antenna tuner takes care of the mismatch at the receiver and transmitter end.  The fed end is about 45 feet up with the mast supported by a small outbuilding at the back of the yard.

This is the antenna that was originally a ground mounted vertical and was then raised above ground to eliminate the ground mounted radials.  It is 33 feet high and had originally been intended as a tuned forty meter amateur antenna but has always worked well on almost any band up through  21 MHz with the use of an antenna tuner.  Six elevated radials the length of the element were also used as guy wires.  Various sizes of aluminum tubing were used for the center element with it guyed at mid level with nylon string which is not visible in the picture.  It is mounted on a ten foot mast.  Unlike the other ground plane antennas which have drooping radials, the radials for this antenna went out horizontally to keep them high enough to allow walking beneath them.  This antenna has performed very well for SWBC from 49 meters through 16 meters.  On higher frequencies, the extra high angle lobes makes it less than optimal for long haul DX on those bands.


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