The first "echo box" I remember hearing on the CB was in early 1977.
A guy calling himself "Wicker Bill" in Englewood, California came
booming in via skip to the East Coast. He was using an analog tape
loop. It sounded ten times better than the cheap reverbs of today.
The second echo box I heard was when my 14 year old friend came on
the air later in 1977 with tons of reverb type echo. I asked him what
he was doing, and he said to come over and he would show me. When I
arrived he had a tin metal trash can over top of his head, and he was
holding his Realistic desk power mic up inside the trashcan with his
head. It was hysterical to see. His entire head was enveloped by the
trash can. I fell over laughing.