How to Construct a Dipole
1. First, find some wire. The gauge isn't critical although it should be strong enough to support its own weight without breaking. The thicker the wire the greater the operating bandwidth of the antenna. Also, some local codes may require a certain gauge wire for outdoor antennas. Often 12 AWG is required. If invisibility is a requirement then use as small as you can get away with. Insulated wire will work fine and in fact I recommend it.
2. Next you will need to cut the wire for the frequency at which you want to operate. The wire needs to be equivalent to a 1/2 wave in length of course and the tried and true formula below will get you in the ball park:
Length (feet) = 468 / Frequency (MHz)
or
Length (meters) = 144 / Frequency (MHz)
or
Length (meters) = 144 / Frequency (MHz)
I usually add a enough extra length to these dimensions to account for whatever I need to wrap around the insulators. Using these dimensions the antenna will usually be close enough to the correct length to work well even without manual pruning of the antenna for lowest VSWR but sometimes other factors can influence the required length. For instance, insulated wire will cause the antenna to need to be a little shorter due to the added dielectric of the insulation. Also, proximity to the ground will create the same effect due to dielectric loading of antenna from the Earth.
3. Find a small sturdy tree or pole and run the wire around it once. Pull the wire around until both ends meet and stretch them tight. While keeping the wires tight, walk up the length of the wire until you reach to tree or pole. Cut the wire on the opposite side from the open ends. You now should have two equal lengths of wire.
4. Find 3 insulators. Dog bone insulators are the easiest to use but just about anything with insulating properties will work such as plexiglass retangles with holes drilled in them, PVC pipe sections, cut-up sections of platic clothes hangers, or whatever else you can find. Just keep in mind the insulators should support the weight of the wire, withstand ultraviolet radiation from the sun, and not absorb moisture. If you plan on using anything greater then about 100 watts of power I would highly recommend high voltage insulators designed for the purpose at the ends of the dipole. The center insulator will only have a small voltage across it and therefore isn't nearly as critical.
5. Now strip, if needed, enough wire to wrap around each insulator and wrap several turns around back onto itself. There should be a wire attached to each end of the center insulator and one insulator to the end of each free wire.
6. This version of the dipole will be fed with coax cable. For 100 ft runs or greater choose RG-8 or similiar for 14 MHz and above and RG-58 for below 14 MHz. For less then 50ft, RG-58 will be adequate for 30 MHz and below. RG-8M style coax will be adequate for up to 100 ft lengths below 30 MHz. Prepare the antenna end of the coax by first cutting the vinyl off of above 4 inches of the end of the coax. Next, with some needle nose pliers reach in between the braids of the outer shield and grap the center conductor and its dielectric. Do this near where the vinyl starts again. You should be able to pull the center conductor out from within the shield. This should leave you with two seperate conductors.
4. Find 3 insulators. Dog bone insulators are the easiest to use but just about anything with insulating properties will work such as plexiglass retangles with holes drilled in them, PVC pipe sections, cut-up sections of platic clothes hangers, or whatever else you can find. Just keep in mind the insulators should support the weight of the wire, withstand ultraviolet radiation from the sun, and not absorb moisture. If you plan on using anything greater then about 100 watts of power I would highly recommend high voltage insulators designed for the purpose at the ends of the dipole. The center insulator will only have a small voltage across it and therefore isn't nearly as critical.
5. Now strip, if needed, enough wire to wrap around each insulator and wrap several turns around back onto itself. There should be a wire attached to each end of the center insulator and one insulator to the end of each free wire.
6. This version of the dipole will be fed with coax cable. For 100 ft runs or greater choose RG-8 or similiar for 14 MHz and above and RG-58 for below 14 MHz. For less then 50ft, RG-58 will be adequate for 30 MHz and below. RG-8M style coax will be adequate for up to 100 ft lengths below 30 MHz. Prepare the antenna end of the coax by first cutting the vinyl off of above 4 inches of the end of the coax. Next, with some needle nose pliers reach in between the braids of the outer shield and grap the center conductor and its dielectric. Do this near where the vinyl starts again. You should be able to pull the center conductor out from within the shield. This should leave you with two seperate conductors.
