at
W4NFR
A few summers back I put up a Half Wave Cage Dipole 40 Meter Antenna. This design
is constructed and marketed by W4HV in Mt. Carmel, Tn. and available for any band. He advertises on the internet.
The Antenna consists of 6 runs of #14 stranded wires spaced evenly around (8) 12" Diameter plastic Hula Hoop spacers made of 3/4" Poly Tubing. The Poly is joined
using a small wooden dowel and Glue. You can make the Hoops 12" 15" 20" it is not critical. Drill the 6 holes and space evenly around the circumference.
Tip: When putting this together, bunch all 4 hoops together, near the feedpoint and feed your wires thru each hoop one wire at a time until all are thru and connected to the common point on the choke. Secure with a split bolt. Slide each hoop into position. Secure the wires at the distant end with a split bolt. Be sure to attach a single 5' wire.
Use PVC and caps for the end insulator and drill large 1/2" holes. Run the tuning stub
along the support rope and ty-rap.
At the Feed point is a RG-8X Current Choke to prevent RF coming back on the
Coaxial feedline.
The Current Choke is made using 22' of RG-8X Coaxial cable wrapped around a 2" Diameter of PVC. Use a Tee on top and cap all open ends. A SO-239 can be mounted at the bottom with a weep hole. The Tee also has caps. Drill 1/2 holes for the wires to go thru. Bring out the split coax to secure to each side of the dipole.
Split Bolts are used to secure all the wires at the ends and the feed point. No soldering.
The antenna has the advantage of being broad banded. It covers the entire 40 meter
band with a SWR of less than 1.7 : 1 and a best frequency of 1.1 : 1 at the middle.
Also, the efficiency is greater than a single wire dipole due to the six wire current distribution.
My antenna is hung off the side of my 40 foot tower as a sloping dipole. It can be installed in about any attitude. Horizontal, Vertical, Slope, Inverted V etc.
A short 5 ft run of wire at the ends is used to fine tune the antenna for the middle of the band. I tie-wrapped the wire to my support rope.
You can build your own or buy from W4HV at his website. With the price of copper, you will have about the same money invested either way!
It has been a real performer for me!
W4NFR
40 Meter Cage Dipole Up 40 feet
RG-8X Current Balun At The Feed
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