are envisioned wherein opposing ribs 550 and 551 are provided by sleeve 520 in these embodiments a split coupling member is provided wherein opposing semi circular coupling members 560 and 561 are positioned on corresponding halves of sleeve 520 semi circular coupling members 560 and 561 may be retained on sleeve 520 by any suitable method such as adhesive bonding or additionally or alternatively held in place by a fixture during manufacturing and held in place by the compressive force between coupling members 560 561 and an outer conductor i e a radiating portion of a microwave antenna assembly the transitions between differing radii may be stepped discontinuous as illustrated in fig4 5 or may be tapered continuous as can be seen in the embodiments illustrated by fig1 et seq as best illustrated in fig1 a and 12b certain embodiments of a high strength microwave antenna coupler 600 include an insulating member 605 which may include a tapered section 621 621 u2032 between sleeve 620 620 u2032 and a shoulder 622 622 u2032 a tapered section as described herein may strengthen insulating member 605 by for example dissipating stress concentrations which may otherwise be formed within insulating member 605 and or reinforcing insulating member.