Frequency hopping
Do you remember actress Hedy Lamarr?
She got a patent on the basis of wifi. (1942)
"frequency hopping, spread-spectrum communication system”
During WWII torpedos were radio controlled
and could be jammed with the right frequency.
They were to use a player piano roll
to change frequency on a predetermined sequence.
It was never placed in use.
Frequency hopping was used on some aircraft radio.
In my early ham radio days,
surplus military radioes were available.
The ART13 had motors to drive the tuning controls.
It had a channel selector A,B,C etc
so that all controls were preset and the channel could be changed on an arranged schedule.
That was the good old days.
Change channel, hear the motors whir,
and you are tuned up on a new frequency.
No one wants that now.
Not enough room for the power supply.
Now, connect your ham radio to the rpi and talk over the internet.
Why, you do not even have to know code anymore.
Who wants to run CW