Dual receivers cause reduced range?
Having had at least 3 rx failures in my 20 years of flying I am a strong advocate of a dual Rx setup in some of my more valuable planes. I have not had any range reduction but I follow the "non parallell" antenna tecqnique descibed here.
Arguments against dual RX's state that adding an extra one inreases the probability of failure which is true. However, the probability of simultaneous failure is very low. If you doubt the soundness of redundant systems/components, look at full size aircraft and the numerous "back up" items carried. Dual magnetos, dual engines, back up pumps, dual or triple hydraulic systems, etc. the list goes on and on. :-)