G'day

Why use more than one receiver?

Have you ever listened to FM radio in a big city. Sometimes the signal bounces off the reflective surfaces and the reflected signal cancels the direct signal and you get what is called "the picket fence effect". That is, the signal strength increases and decreases greatly over short distances because of the reflections. The result is a sort of chopped sound from the radio. It fades in and out over short distances. The same effect can be heard with UHF transceivers in a reflective environment - the signal fades in and out rapidly as you drive along. You get a sort of FFFFFT FFFFFFT FFFFT sound as the muting circuit in the radio cuts in and out.

The same thing can happen with any radio transmission and the higher the frequency, the closer together are the cancellations or nulls as they are called.

So, one solution to a fading in and out signal is to use "diversity tuned receivers". This is a system where two or more receivers are joined together by a diversity system which picks the strongest signal from the receivers to process and send on to the decoder. This system is used in high end FM radio receivers intended for cars and also by the military where they need rock steady reception particularly for data.

This is the reason for the two receivers in some Spektum systems. It is a "belt and braces" approach to minimising the signal cancelling problems caused by multipath reflections which are very common with high frequency radio transmissions.

If you are out in the middle of a paddock where there are no reflecting surfaces then it is probably not necessary but if there are metal buildings or large car parks or metal grain silos etc etc, then it starts to make sense.