For preventing reflections when the frequencies are higher or close to the transmission line length, for a 50 Ohm coaxial cable a 50 Ohm termination resistor is recommended.
I also used to think/know that source output impedance Rs also needs to be 50 Ohm. But recently I have read in a forum or a text(I'm sorry that I cannot find it at the moment where), someone was mentioning that the source output impedance Rs doesn't have to be 50 Ohm and it is enough only coax characteristic impedance and the Rin are equal/matched.
Is that correct? Can Rs be anything other than 50 Ohm safely?