|Working All Duluth
List of Duluth Parks
Ground Snake Antenna
|On the right is the current version of my
end fed dipole where I use a toroid choke to reduce the
bulk and improve the effectiveness over an air core
choke. From left to right:
feed-line extension with common mode choke, feed
line, common mode choke, coax antenna arm, single wire
antenna arm, throw line.
Note please that in the photo of the antenna the wires are flaked not coiled for storage and Velcro bands are used to secure the bundles.
If one tries to coil the wire the result is a twisted, tangled pile of wire that takes a long time to straighten out, untwisting the coils one put in earlier.
Flaking is fast and easy and allows a quick, almost trouble free deployment of the antenna. Watch for possible hitches toward the ends if one happens to form.
|This is my present common mode choke made
with an FT240-43 toroid.
The choke is a critical part of this antenna design since it defines one arm of the dipole.
*One reference to choke balun construction can be found here: http://www.karinya.net/g3txq/chokes/
Another here: A Ham's Guide to RFI, Ferrites, Baluns, and Audio Interfacing Revision 5a 5 Jun 2010
© Entire Contents Copyright 2007-10 The Audio Systems Group, Inc., except Appendices 2, 3, and 4, which are property of the cited authors, and product data, which is copyright by Fair-Rite Products. All Rights Reserved
by Jim Brown K9YC
Audio Systems Group, Inc.
In the August, 1991 QST, available
on the ARRL archive, is an article on the end fed
dipole titled: RFD-1 and RFD-2: Resonant Feed line
attracted to the end-fed dipole because it is
lightweight, compact, easy to hang and take down,
and with a tuner
performs well on more than one band.
With and under-hand toss this system works for about a 30 foot maximum height. It is compact and easy to carry. The joint between the coax and the single wire needs to be strong and capable of sliding through tree branches without getting hung up. I twist and solder the wires, then seal with multiple layers of shrink tubing.
I have not figured a way to streamline the choke. When I pull the antenna up I just hope that the coil can get high in the tree before a branch stops it.
|Update: October 13,
Today I took the rig out to Park Point on
Minnesota Point (Duluth, Mn) for an afternoon
of "Radio in the Park" using the end-fed
dipole. I found a comfortable place to set
up along the shore where a large Cottonwood
tree, mostly free of leaves, provided tall
support for the antenna. Now, this year I
have been using a 6 foot walking stick, cut from
an invasive Buckthorn bush, during my hikes in the
woods. A hiking stick I find gives me added
stability on rough trails and helps on steep
accents and decents; plus, with a notch carved in
the small end it makes a great throwing tool for
my weight and throw line. With a bit of
practice I was estimating I could about double the
height I could throw the weighted line up in a
tree. So today with that large Cottonwood in
front of me I hooked the weight, eyeballed the
branch I wanted and let fly with a two-handed
toss. First try the weight goes over the
proper branch and makes it to the ground and I
grab the weighted end and pull the dipole up into
the tree. The chokes do not get hung up
allowing the end to be pulled to the highest point
at which time I notice the bottom end is hanging
free in the air. That makes the top 65 feet
up! Not bad for archaic, stone age
technology applied to the 21st century.
have compared the End-Fed to my 14 foot ground
mounted vertical and to my car mounted vertical on a
number of occasions and it works about as well,
sometimes better, especially over rock where a
vertical loses out because of poor soil
If there is not a tall tree handy I lay it on
bushes, maybe 4 or 5 feet off the ground and it
works well. I have even laid it on the snow,
continuing a qso that started with the antenna high
in tree then taken down and I laid on the snow. My contact
did say the signal strength went down some.
an LDG auto tuner in my portable kit because so far
the end-fed dipoles do not show a low swr on the
band it is cut for.