to the base of the antenna mast and link unit 131 bracket 28 comprises respective side members 28a 28b which are spaced apart 13 62 inches so as to receive the tapered ends of the side members of link unit 131 pivot bolts 138a are passed through corresponding bores formed in the side members of brackets 28 and link unit 131 pairs of travel limit pins 131f and 131g are provided through respective sides of the tapered ends 131e of link unit 131 these pins cooperate with semicircularly relieved areas 28d 132g in the respective ear sections of the side members of bracket 28 and link unit 132 to limit the pivotal excursions about pivot pins 138a each of the pivots of link unit 131 is constrained for maximum excursion of about 46 u00b0 in either direction from the straightened position for the joint the maximum allowable angular excursions in one direction are illustrated in fig3 it has been found that limiting the bend to less than 46 u00b0 for the disclosed joint configuration results in a rugged linkage able to withstand repeated movement in the preferred embodiment pins 131f and 131g are fabricated from 0 500 inch diameter steel pins the pins at the maximum travel contact corresponding semicircular relieved.