Somewhere in another forum, I summarized the story of frequency hopping. It was originally patented by the actress Heddy Lamar and her husband or boyfriend during WWII. Too long of a story to repeat again, but it was finally used by the US government during the Cuban missile crisis.

For those wanting to go back to 72 mHz, the train has left the station. As far as I know, no major manufacturer makes anything, except maybe a few receivers on 72. The market has moved to 2.4. People looking for a perfect system are in the wrong hobby. I started with escapements on 27, then galloping ghost, color flag 72 and then the narrow channel 72. The best has been 2.4. My only crash with 2.4 was a battery pack that decided to have a cell short out in flight and can;t blame that on 2.4