07-21-2015, 01:17 PM
according to my copy of the NEC (1947), for outdoor installations:
3404. (8111) Conductors. Antenna, counterpoise and lead in conductors shall be of hard drawn copper, bronze, copper clad steel, or other high strength, corrosion resistant material. Soft drawn or medium drawn copper may be used for lead in conductors where the maximum span between points of support is less than 35 ft.
3405. (8112) Supports. Outdoor antenna and counterpoise and lead in conductors shall be securely supported. They shall not be attached to poles or similar structures carrying electric light or power wires, or trolly wires of more than 250 volts. Insulators supporting the antenna or counterpoise conductors shall have sufficient mechanical strength to safely support the conductors. Lead in conductors shall be securely attached to the antenna.
3406. (8113) Clearance from Other Conductors. Outdoor antenna, counterpoise and lead in conductors from an antenna to a building shall not cross over electrical light or power circuits and shall be kept well away from all such circuits so as to avoid the possibility of accidental contact. Where proximity to electric light and power service conductors of less than 250 volts cannot be avoided, the installation shall be such as to provide a clearance of not less then 2 ft.
It is recommended that antenna and counterpoise conductors be so installed as not to cross under electrical light or power conductors or trolly conductors.
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3415. (8121) Size of Antenna and Counterpoise. Outdoor antenna and counterpoise conductors for receiving stations shall be of a size not less than given in the accompanying table.
Material Minimum size of conductors when maximum open span is
Less than 35 ft. 35 to 150 ft. Over 150 ft.
Hard drawn copper 19 14 12
Copper clad steel, bronze, or other high strength
material 20 17 14
3416. (8122) Size of Lead In. Lead in conductors from outside antenna and counterpoise for receiving stations shall, for various open span lengths, be of such size as to have a tensile strength at least as great as that of the conductors for antenna as specified in section 3415. When the lead in consists of two or more conductors which are twisted together, or are enclosed in the same covering or are concentric, the conductor size shall for various maximum open span lengths, be such that the tensile strength of the combination will be at least as great as that for the conductors for antenna as specified in section 3415.
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3422. (8141) Arrester. Each conductor of a lead in from an outdoor antenna shall be provided with a lightning arrester approved for the purpose, except where the lead in conductors from antenna to entrance to building are protected by a continuous metallic shield which is permanently, and effectively grounded. Lightning arresters shall be located outside the building, or inside the building between the point of entrance of the lead in, and the radio set or transformers, and as near as possible to the entrance of the conductors to the building. The lightning arrester shall not be located near combustible material nor in a hazardous location.
In addition to these things I recommend using a glass insulator at every point where the antenna conductor will be supported so that it does not become shorted to ground in wet weather. I much prefer using stranded wire for outdoor antennas. It is more flexible, and suffers less stress weakening over the years than a single strand wire does. One can use either insulated or non-insulated. For shorter runs, 35 ft. or less I use 16 gauge or 14 gauge, and 14 gauge for 35 ft to 150 ft. I have never put up an antenna longer than 150 ft so far, but would use at least 12 gauge stranded for that.
3404. (8111) Conductors. Antenna, counterpoise and lead in conductors shall be of hard drawn copper, bronze, copper clad steel, or other high strength, corrosion resistant material. Soft drawn or medium drawn copper may be used for lead in conductors where the maximum span between points of support is less than 35 ft.
3405. (8112) Supports. Outdoor antenna and counterpoise and lead in conductors shall be securely supported. They shall not be attached to poles or similar structures carrying electric light or power wires, or trolly wires of more than 250 volts. Insulators supporting the antenna or counterpoise conductors shall have sufficient mechanical strength to safely support the conductors. Lead in conductors shall be securely attached to the antenna.
3406. (8113) Clearance from Other Conductors. Outdoor antenna, counterpoise and lead in conductors from an antenna to a building shall not cross over electrical light or power circuits and shall be kept well away from all such circuits so as to avoid the possibility of accidental contact. Where proximity to electric light and power service conductors of less than 250 volts cannot be avoided, the installation shall be such as to provide a clearance of not less then 2 ft.
It is recommended that antenna and counterpoise conductors be so installed as not to cross under electrical light or power conductors or trolly conductors.
..............
3415. (8121) Size of Antenna and Counterpoise. Outdoor antenna and counterpoise conductors for receiving stations shall be of a size not less than given in the accompanying table.
Material Minimum size of conductors when maximum open span is
Less than 35 ft. 35 to 150 ft. Over 150 ft.
Hard drawn copper 19 14 12
Copper clad steel, bronze, or other high strength
material 20 17 14
3416. (8122) Size of Lead In. Lead in conductors from outside antenna and counterpoise for receiving stations shall, for various open span lengths, be of such size as to have a tensile strength at least as great as that of the conductors for antenna as specified in section 3415. When the lead in consists of two or more conductors which are twisted together, or are enclosed in the same covering or are concentric, the conductor size shall for various maximum open span lengths, be such that the tensile strength of the combination will be at least as great as that for the conductors for antenna as specified in section 3415.
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3422. (8141) Arrester. Each conductor of a lead in from an outdoor antenna shall be provided with a lightning arrester approved for the purpose, except where the lead in conductors from antenna to entrance to building are protected by a continuous metallic shield which is permanently, and effectively grounded. Lightning arresters shall be located outside the building, or inside the building between the point of entrance of the lead in, and the radio set or transformers, and as near as possible to the entrance of the conductors to the building. The lightning arrester shall not be located near combustible material nor in a hazardous location.
In addition to these things I recommend using a glass insulator at every point where the antenna conductor will be supported so that it does not become shorted to ground in wet weather. I much prefer using stranded wire for outdoor antennas. It is more flexible, and suffers less stress weakening over the years than a single strand wire does. One can use either insulated or non-insulated. For shorter runs, 35 ft. or less I use 16 gauge or 14 gauge, and 14 gauge for 35 ft to 150 ft. I have never put up an antenna longer than 150 ft so far, but would use at least 12 gauge stranded for that.
