Wire Vertical Antennas, Supported by Fiberglass Poles
VERTICAL ANTENNAS WITH TOP-HAT WIRES
CAN HAVE LETHAL HIGH VOLTAGE NEAR THE ENDS OF THE WIRES.
KEEP OUT OF REACH OF HUMANS AND ANIMALS !!!
have low angle radiation patterns, even when they are mounted close to the ground. This makes them well suited for working DX, provided attention is paid to the ground around them.
require a good radial network to be effective, but that can be achieved with just 16 ground-mounted radials , or just 4 elevated radials (more is better, of course). Even just half that many (8 ground, or 2 elevated) radials will provide good results.
are twice as long, but do not require an extensive radial network to be effective. However when mounting this type of vertical near the ground, its feedpoint should be elevated at least one meter, preferably two meters (4 to 7 feet) above the ground. Half-wavelength verticals have HIGH VOLTAGE near the feedpoint. It is important that humans and animals cannot touch this part of the antenna. The disadvantage is, the feedpoint impedance is very high (about 2K to 3K Ohms), and this must be matched to 50 Ohms.
are (best case) 1/2 wavelong, and fed in the middle with 50 to 70 Ohm coax. These have the advantages of needing no radials, no special matching at the feedpoint, and they typically have about 5 degrees lower takeoff angle than the quarterwave vertical. Disadvantage: the feedpoint is half way up the antenna, which can present mechanical difficulties. NOTE: When fed with lightweight twinlead, such as 300 Ohm ladderline, and matched in the shack with a matchbox, these make good multi-band antennas. In this case it is OK to shorten the dipole, even as much as just 1/8 wavelength, as long as you have a good quality matchbox.
Vertical Dipole Arrays
4-SQUARE Vertical Arrays
See: G4ATA's 4-SQUARE
Horizontal Antennas Comparison
For comparison, horizontal antennas must be at least 1/4 wavelength high to even begin to be effective for DX, and 1/2 wavelength is the minimum height to be sure they work well for DX. They work well for NVIS at lower heights, but not for DX.
For our lower ham bands, 160, 80 & 40m,
the heights required by horizontal antennas for working DX is effectively beyond the reach of most hams. As a result, we often turn to vertical antennas for our DX solution.
Most of the verticals presented in this section,
especially the ones built on Spiderbeam fiberglass poles, have been field and contest proven by tens of amateurs. In this section, I will show you how easy it is to build an effective DX vertical antenna for any of the low bands.
Note: the verticals I present here are very simple to build and are quite effective. I am not saying that they cannot be improved upon by adding more radials, or better matching . . .
BUT I STRONGLY STATE THAT THEY WORK VERY WELL FOR DX,
COMPARED TO A LOW HANGING HORIZONTAL ANTENNA
OR COMMERCIAL MULTI-BAND TRAP VERTICALS.**
**ASSUMPTION: The antennas are erected in the clear. If they are in between a bunch of houses or other objects, it is difficult to predict how anything will perform, regardless if it is a commercial or home-brew antenna.
CHOOSE AN ANTENNA FROM THE MENU ON THE TOP LEFT.