I agree with this. I have tried many different pre-amps and splitters. I keep going back to my Stridesbergs. They are by far the best and worth the extra expense.This Multicoupler is what you need for best results. Works very well with 4 scanners.
4 Port MCA204M VHF/UHF Receiver Multicoupler - 25 MHz to 1 GHz | Scanner Master