An alkali-free glass consists essentially of, in mass percent, 58-70% SiO2, 10-19% Al2O3, 6. An elongated needle 14 having a proximal end 16 is attached to the hub 12. A second receiver is coupled to the antenna system and receives and processes request signals from a second unit type at a disparate second frequency. The method may also include applying a given one of a plurality of Modulation and Coding Schemes to the frame to produce a modulated frame, wherein the given one of the plurality of MCSs is selected based, least in part, upon the spectral shape corresponding to the identified temporal region.