40m Vertical on a 12m Spiderpole
[ elevated radials ]
For people (like me) who hate fussing with radials.
In the drawing above, the radials look shorter, but they are the same size as the radiator wire.
I have lived in at least 25 different houses or appartments since I was licensed in 1962. Most of my life I have rented my house or appartment, I was not the owner. When I install an antenna, I know it is not going to be perminant. In these cases, I find it more convenient (and cheaper) to use elevated radials.
ELEVATED RADIALS ARE RESONANT, AND MUST BE MEASURED ACCURATELY.
You need about 8x as many ground mounted radials to equal the effectiveness of elevated radials. In other words, just two elevated radials will work about as effecient as 16 ground mounted radials. 3 elevated radials works as efficient as 24 ground radials, etc. Adding the 3rd elevated radial will give you a slightly more symmetrical radiation pattern than with just 2 elevated radials, but the 3rd radial may be viewed as a luxury.
IMPORTANT: ALL ELEVATED RADIALS MUST ALL BE EQUAL LENGTH, AND EXACTLY 1/4 WAVELENGTH LONG.
When using two radials, they should be in a straight line. When using 3 or 4 radials, they should be spaced symmetrically around the antenna. In a pinch, it is even OK to use just one elevated radial. The effeciency is not quite as good and the radiation pattern will be skewed a little, but the antenna will still work quite well.
Note: Although the antenna works OK with just one elevated radial, it is NOT sufficient to use just one ground mounted radial. Verticals with ground mounted radials need at least 4, better 8 or more radials to be efficient.
The antenna presented here is neither better, nor worse than a standared quarter-wavelength vertical which uses ground radials. It's just a different way of installing the quarter-wave vertical.
For Campers: This version of the 40m vertical antenna is also good for using at places like campsites where radials would be laying on the ground, and not burried. Pedestrians walking around the vertical can easily trip over ground mounted radials, but can walk under the elevated radials.