MIMO and Smart Antennas for Mobile Broadband ... - 4G Americas

The weight and moment (torque) resulting from this wind load integrated over the 30 meters of mastheight are tabulated below:Twelve 1-1/4” LCFS114Coax Cables For 4branches/sector6 Typical2xpol Antennas3 Typical RemoteRadio HeadsWeight 330 kg 2x3x 15 kg = 90 kg 3x 17 kg = 51 kgMoment 136 kNm 120 to 170 kNm 15 to 22 kNmThe representative antenna had an area of 0.48 m 2 and the Remote Radio Head (RRH) was exemplifiedwith an area of 0.118 to 0.18 m 2 . The moment is generally proportional to the area and to the square ofthe wind velocity. Keep in mind, too, that 2 branches per sector would amount to half the weight and ashalf the moment.In addition, ice can accumulate on the cables and hardware, doubling the weight and adding to theeffective area. In Table C.1 of the TIA-222-G standard, the impact of two different thicknesses of ice isprescribed for a 9-antenna configuration along with nine 1-5/8” cables configuration. This is a compositeof all the antennas and cables together. (Note that the cables here are larger than the earlier example.)Table 5 – Example wind load for a 9 antenna (and 9 cables) tower with ice loading.9 antennas9 1-5/8”No IceICEThickness ≤ 0.5”ICE0.5” ≤ Thickness ≤ 1.5”Eff. Area Weight Eff. Area Weight Eff. Area Weight6.5 m 2 337 kg 7.9 m 2 337 kg 10.2 m 2 693 kgScaled 6/9 4.3 m 2 225 kg 5.3 m 2 225 kg 6.8 m 2 462 kgMoment 182 kNm 222 kNm 285 kNmThe important comparison is that remote radio heads have less than 1/13 th the weight and 1/6 th to 1/9 ththe moment in high wind bursts. Icing and larger cables such as 1-5/8” make the comparison even morestrikingly in favor of RRHs.Both self-supporting and guyed masts are susceptible to ice and wind, but of course monopoles withcables inside the single hollow tube, shield the cables from icing and wind, but in monopoles, access tothe cables is more difficult and constrained by size limits as all must fit through access holes such asthose in the following photo in Figure 72.4G Americas MIMO and Smart Antennas for Mobile Systems – October 2012 – All Rights Reserved98