Antenna: 75 meters, Range: 3.6 to 4 MHz
Good 75 meters antennas are easy to build with nothing more than readily available materials. Since 75 meters covers the frequency range of 3.6 to 4 MHz you can use a few algebraic formulas to compute antenna sizes.
As you can see, the size of a quarter wave antenna for 75 meters is rather large at almost 64 feet for 3.665mhz. For survivalist use a vertical antenna for 75 meters is impractical while a dipole for 75 meters could be quite useful. The band known as 75 meters is actually part of the 80 meter band but is designated as voice only.
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 75 meters is approximately 63 feet 10 and 3/16 inches in length. This antenna measurement can be used for either a vertical antenna for 75 meters or a horizontal antenna for 75 meters.
75 meters is a great band for regional interstate and intrastate communications. It is quite capable of good intercontinental communications as well but generally requires an amplifier to do so. 75 meters and even 80 meters should also be a part of a survivalist communication system.