Certain characteristics of the frequency range 275-3 000 GHz combine to reduce the likelihood of interference between the radio astronomy service and active services in this range. The purpose of this Report is to present a basic introduction to those characteristics and how they affect potential sharing scenarios. Based on the analysis in this Report, there is little chance for interference to radio telescopes from co-frequency terrestrial, airborne, or satellite transmitters, particularly at frequencies above 1 000 GHz. The results of this study are applicable to current and future discussions relating to extending No. 5.565 of the Radio Regulations to frequencies in the 275-3 000 GHz range, and studies related to the advancement of technology at frequencies above 275 GHz 1.