What is the best frequency to use?
For industrial or commercial controls, the 900 MHz frequency band is preferred.  Almost all electrical equipment radiates some noise, especially during starting and stopping. The electrical noise is most noticeable at lower frequencies and can cause sporadic operation of 49 MHz radio control equipment, whereas the noise is almost imperceptible at 900 MHz  At higher frequencies, the radio waves become more directional and do not propagate around obstacles as well.