Long delayed radio echoes

This thesis describes an experimental program carried out at Stanford over a five-year period. The experiment involved transmitting a radio signal, and tape-recording the output of a receiver gang-tuned with the transmitter for the following 30 s interval. The tapes were later audited for possible LDE. Although none of the possible LDE received reproduces exactly the transmitted signal, many exhibit features that seem unlikely to have been generated except by an LDE mechanism. A mechanism for producing LDE has been studied which involves signal propagation in an electron plasma wave mode at very low group velocity. Modifications to the simplified theory leading to prediction of longer delays are discussed