Antenna: 40 meters, Range: 7.0 to 7.3 MHz
Good 40 meters antennas are easy to build with nothing more than readily available materials. Since 40 meters covers the frequency range of 7.0 to 7.3 MHz you can use a few algebraic formulas to compute antenna sizes.
Antennas for 40 meters are used as verticals and dipoles with great success. 40 meters antennas are a bit large as verticals but dipoles for 40 meters are quite manageable. A dipole for 40 meters can easily be strung between two tall trees located near a survivalist camp.
This formula: 234/f can be explained by dividing 234 by the desired frequency in megahertz which will give you the length, in feet, of a 1/4 wave antenna. This formula isn't exact in that it assumes the radiating element is infinitely small. What this means is if the radiating element was one inch in diameter then the resonant length of the antenna would be a little shorter than the calculated one given by the formula gives you.
Using the formula above you will soon see that an antenna for 40 meters is approximately 32 feet 6 and 9/32 inches in length. This antenna measurement can be used for either a vertical antenna for 40 meters or a horizontal antenna for 40 meters.
Propagation is very good on 40 meters for local and DX work. Intercontinental contacts are very common on voice, Morse code and the digital modes. Of all the bands available it might be said that 40 meters is the most versatile.