  We have measured the in situ average electric field attenuation length for
radio-frequency signals broadcast vertically through the Ross Ice Shelf. We
chose a location, Moore Embayment, south of Minna Bluff, known for its high
reflectivity at the ice-sea interface. We confirmed specular reflection and
used the return pulses to measure the average attenuation length from 75-1250
MHz over the round-trip distance of 1155 m. We find the average electric field
attenuation length to vary from 500 m at 75 MHz to 300 m at 1250 MHz, with an
experimental uncertainty of 55 to 15 m. We discuss the implications for
neutrino telescopes that use the radio technique and include the Ross Ice Shelf
as part of their sensitive volume.
