one thing to remember is cable loss is linear.....there are no peaks and valleys in transmission. first, check the output then input of your 1st amp out. if you see a difference, then there you go. i have worked on countless amps that are "rated" for 1 GHz, but contain 550, 750 and 870 plug-ins. As someone said before, also check your stock....those fuckers in the warehouse have no clue what is what....yes? I woul;d find myself a known good module to carry around and use when I think something is not quite right. Those modules are GOLD, guard them with your life...:)