When determining how long to make each leg of a Dipole antenna, dividing the frequency in Megacycles into 468 will give the overall half wave length of the antenna. To find the quarter wave, divide that number by two. This will give you the length of each leg of the antenna.

Example — 80 meters : If you are operating on 3.8 megacycles, dividing 3.8 into 468 gives 123.16 feet over all. To find the quarter wave, dividing 123.16 feet by 2 gives 61.58 feet for each leg. Cut the wire two or three feet longer so you will have some to fold back on itself when adjusting the SWR. The part that folds back on itself does not effect anything. Connect the co-ax at the center point or middle of the antenna, the center lead of the co-ax to one leg and the braid to the other leg. When adjusting for minimum SWR, adjust each leg the same amount, current fed.

Example — 40 meters : If you are operating on 7.2 megacycles, dividing 7.2 into 468 gives 65 feet over all. To find the quarter wave, dividing 65 feet by 2 gives 32.5 feet for each leg. Cut the wire two or three feet longer so you will have some to fold back on itself when adjusting the SWR. The part that folds back on itself does not effect anything. Connect the co-ax in the center point or middle of the antenna, one leg to the center lead of the co-ax and the braid to the other leg. When adjusting for minimum SWR, adjust each leg the same amount, current fed.

Example — 20 meters : If you are operating on 14.5 megacycles, dividing 14.5 into 468 gives 32.28 feet over all. To find the quarter wave, dividing 32.28 by 2 gives 16.14 feet for each leg. Cut the wire two or three feet longer so you will have some to fold back on itself when adjusting the SWR. The part that folds back on itself does not effect anything. Connect the co-ax in the center point or middle of the antenna, one leg to the center lead of the co-ax and the braid to the other leg. When adjusting for minimum SWR, adjust each leg the same amount, current fed.

Example — 2 meters : If you are operating on 144.5 megacycles, dividing 144.5 into 468 gives 3.24 feet over all. To find the quarter wave, dividing 3.24 feet by 2 gives 1.62 feet for each leg. When mounting on a vehicle, a quarter wave antenna MUST be mounted on a metal base. A quarter wave antenna can be mounted on a fiberglass or plastic body vehicle with the co-ax connected to one end of the antenna, center lead to antenna, braid grounded, voltage fed.

For more information, please see the following link: http://en.wikipedia.org/wiki/Dipole_antenna

The following form may be used to calculate the optimal antenna length for a specific frequency.