I wish to set up a wireless mic system in a church and require a receiver that will receive and process four different transmitter frequencies and mix the output. I wish to avoid four separate receivers with four separate antenna systems and four separate power supplies. Does such a creature exist?
There are receivers called "dual" (two receivers in one enclosure) and called "quad" (four receivers in one enclosure.) Note that the audio signal from a "dual" or a "quad" are not mixed together; they emerge as individual signals.
For educational material about wireless systems, read our booklet "Selection and Operation of Wireless Microphone Systems".