"Richard Harrison" wrote in message
...
Wayne wrote:
"The time deay approach werked well, but never caught on commercially."

Our receiver selection boxes were made by Crosby or Pioneer if I
remember, but it`s been a half century.

Best regards, Richard Harrison, KB5WZI

Heh heh. Yeah, long time.
We made our own time delay box under Navy funding. In a prototype, we
provided the time delay by recording the RTTY signal on tape and playing it
back soon afterwards on a different tape head. The original and delayed
were then sent on different sidebands. Noise was simulated with recorded
static, and the noise audio was injected at the receiving end before
deconstructing the delay with another tape deck.

IIRC, we found combinations that gave about a 3-5 db improvement. Fun
project that would be even more fun with modern circuitry.