// Cantenna external diameter
D = 100;
// Bracket height
H =  8;
// Stand height
StH = 25;
// Wall thickness
T = 1.6;

difference() {
    union() {
        cylinder(d=D+T*2 ,h=H);
        linear_extrude(H) polygon([
          [ -D*0.6, -D/2-StH ],
          [  D*0.6, -D/2-StH ],
          [  0,           D/4         ],
          [ -D*0.6+1.5*T , -D/2-StH+T ],
          [  D*0.6-1.5*T,   -D/2-StH+T ],
          [  0,                D/4-1.4*T           ],
        ],
        [[0,1,2],[3,4,5]], 10
        );
        linear_extrude(H) polygon([
          [ -D*0.25, -D/2-StH ],
          [  D*0.25, -D/2-StH ],
          [  0,             D/4         ],
          [ -D*0.25+T , -D/2-StH+T ],
          [  D*0.25-T,   -D/2-StH+T ],
          [  0,                   D/4                      ],
        ],
        [[0,1,2],[3,4,5]], 10
        );
    }
    translate([0,0,2]) cylinder(d=D,h=H);
    translate([0,0,-1]) cylinder(d=D-2*T,h=H);
}