Do I need to install RF terminator at the end of RF attenuator? Let's say that max power output for RM port is 50W and I'm using 100W 50dB attenuator. What if I was using 50W 40dB attenuator? Is there a possibility that without proper RF load some power may reflect from the end of attenuator?
If your attenuator is beefy enough, you should be fine without a terminator. If a signal does bounce off and come back, it will be attenuated by 2x the value of the attenuator since it passes through the attenuator twice. Say, if you have a 50 dB attenuator, a signal that passes through the attenuator and reflects back should be attenuated by 100 dB. So some will reflect, it's just a question of whether it is small enough to cause a problem or not. 100 dB return loss is pretty darn good even for a terminator. The return loss of a loose connector is probably worse than that.