The paper gives measurements of the velocity of electromagnetic wave propagation in sea ice, the tangent loss, and the specific absorption obtained by means of coaxial-line experiments, assuming sea ice to be the dielectric. Measurements have been made at frequencies of 30, 60, 100, 200 and 400 MHz by pulses of 0.05 and 0.5 ms and video pulses of 0.02 ms at a repetition frequency of 10 kHz, with temperatures from —40° C to —10° C and salinities 17, 8.6, 4.4 and 0.56‰. Data obtained on the values of the tangent loss are in a good agreement with those obtained by Addison. The velocity has been found to be constant (170 m/ms) for radio and video pulses in the ice at any salinity value and temperatures below —22° C. At higher temperatures the velocity decreases being more pronounced with the salinity increase. Data on electrical characteristics of sea ice averaged throughout the ice thickness are presented. These measurements have been made by using long lines, frozen into the ice. Experimental radio-echo soundings of sea ice carried out at the drifting stations SP-19 and SP-21 in 1971-72 and 1972-73 by means of pulsed radar systems in the range 200-100 MHz are also discussed.