A $5.00 40 Metre Vertical That Works !! By: Robby, VY2SS September 29, 2009
Pictures (Click to Enlarge)
40 Metre Vertical Antenna
Feedpoint and Radials
Radiator (center of picture)
Antenna Base
Antenna Base
It is just an elevated wire vertical which consists of an elevated feed point 8 to 12 feet above ground and 4 radials the same length sloping from the feed point to the ground. I usually add rope to the ends of the radials to keep the ends a bit higher.
Four radials at 8 to 12 feet are supposed to be equivilent to 120 on or in the ground. (US Department of Naval and Oceanographic Research). I have been using them for many years and can attest to their usefullness as a DX antenna that costs practically nothing. The most expensive component is the SO-239 connector that I use to connect the coax. (ALWAYS use a PL-259 on the antenna end of the coax. If installed properly they provide a strong electrical and mechanical connection that is waterproof. See below). This connector is mounted on a small piece of scrap aluminum 2 or 3 inches square (or round if you like). The radials are connected to the aluminum and the vertical element is connected to the center pin of the SO-239. Some form of strain relief needs to be devised as the solder in the pin will not hold the wieght of the coax for long. I use a ceramic stand off on the aluminum plate to provide an instulated connection point. (photos available). The coax should drop straight down from the feed point as far as possible. Make sure there are no other antennas or support wires or guy cables that are at or near the electrical length of the vertical element as they could suck power from your antenna and alter the radiation pattern.
Naturally this antenna needs a support. I supported an 80M version from a large cottonwood at my last QTH. This 40M one hangs from a rope that angles down from the top of my 56 foot tower to my neighbors flagpole. A couple of big trees will work or a big one and a smaller one. A pulley at the large one would be usefull to lower it for maintenance or temporary removal. Mine usually won't make it through an ice storm but it is easily repaired.
I have used this same type of antenna in vertical arrays (square four)on both 80M and 40M with the Comtex control box as well as two element phased arrays using coaxial phasing lines. As Bill can testify it shakes you up a bit when you hit the switch on the 40M SQ4 and the US KWs disappear and the Europeans get loud. This is basically four of the verticals described above arranged in a 1/4 wave square with a phasing control box remotely switched from the shack. I have more on this if you want it.
This antenna is simple, cheap and effective but as I mentioned it has a low takeoff angle which makes it good for DX but marginal for regional communications. I plan to supplement my 40M vertical with a low dipole antenna that has a higher take off angle. Even though the polarization will be opposite (reduced coupling), I would like it to be at least 60 feet away. Then I can start reeling in those multipliers in the Maritimes and NF that are in my vertical's skip zone.
By the way, if your coaxial cable's shield or center conductor is black or discolored rather than a bright copper or silver color it has been contaminated. Any water that enters the coax whether from an improperly installed connector or the lack of one altogether or a nick in the black vinyl jacket will ruin the feedline. The conductors, especially the braid will wick the water far into the coax. If you see the braid or center conductor is even partly black then chop ten feet off and inspect it again. Keep hacking it off until you find 100 percent shiney copper. You may wind up with a short cable but it will be a good cable. I have seen it travel 100 feet inside a coaxial cable. Don't save contaminated cable and don't give it to a friend. Throw it out or give it to a CBer. Awlays have your coax sealed.
The same thing can happen to your rotor control cable but you don't need to toss that one. Just strip a 1/2 inch of instulation off each blackened wire and splay the wire strands. Swish them around in battery acid for a minute then rinse in warm water and dry the end of the cable. Then you will have shiney copper ends and you can install crip on spade connectors and solder them.
A good article on installing coax connectors by W8WWW can be found at:
You don't need all the fancy tools he that he has but most are already in your toolbox. I use a box knife instead of strippers and a Weller 140W solder gun.
Updated July 28, 2010 by Scott Nichols VE1OP Please report any errors, omissions or comments to webmaster: snichols[at]mvosprey.com
