> You may say "But nyquist says you can't transmit or receive frequencies at more than 1/2 the sample rate (40 MHz in this case). To a degree that is true. Some

> You may say "But nyquist says you can't transmit or receive frequencies at more than 1/2 the sample rate (40 MHz in this case). To a degree that is true. Some people thought it may be overtones, but what happens in reality something stranger happens. Everything you transmit is actually mirrored around 1/2 the sample rate (40 MHz). For anyone interested this is called aliasing. If you've ever noticed wheels going backwards in racing or train footage, this is exactly what's happening: the wheel's angular velocity is above half the sampling rate (i.e. the camera's FPS), producing a mirrored version which in turn appears to rotate backwards.