how many coax cables does one need from a satellite dish, Lnb, to operate three recivers and tvs?

Answer 1

One coax cable to each LNB ..

Answer 2

That depends on the system. Best guess is 5- 2 from the dish to a multi switch, then one each to the receivers, then maybe one more each from the receiver to the TV (unless you use some other cabling there).
Some newer dishes have the multi switch built into the dish, and the cables may be run directly to the receivers in this case.

Answer 3

i think.it may be depending on the transpounder capasity..whick capasity of transfounder u want. some cables..offers diffrent bandwidths.