RE: Strength of signal and 3IM
I am suprised to hear that IM was ever a significant problem. I don't understand why IM was a problem in the past and not now. I don't see that narrow-banding the receivers should improve IM as IM occurs exactly on frequency. IM products, while always there, should be thousand, more likely millions of times weaker than the transmitter signals. Maybe I'm just not understanding it.
Could it be that in the past IM was confused with something else? Maybe another transmitter operating on the image frequency of a receiver?