The emerging 5GHz unlicensed bands in Europe and the US may be used to support short range, high rate links for portable computers. This would overcome the range and directionality limitations of today's infra-red connections. This paper investigates the performance of a binary FM link in this application, operating in a dispersive indoor channel. The consequence of increasing the modulation index is explored as a cost free means of multipath mitigation. An increase from 0.5 (MSK) to 1 was found to yield a worthwhile improvement in tolerable delay spread. Increasing the index beyond 1 gave no further improvement but significantly affected the spectral occupancy of the signal. This defines a precise design point for high rate, short range radios.5 Pages