You can try all types of testing. You can stand on your roof holding a coat hanger on your left arm while your right touches the chimney, you can wrap yourself in RG58 antenna cable and hold a garbage can lid, or, if there are any issues at all with simulcast, and if you want to be prepared for the future, then an SDS 100 or 200, in my opinion, would cause you the least worry and assure you good service for many years. For me the answer was simple. I had so much simulcast interference here neither my 436 nor 536 would work. The SDS 100 broke thru all that. I have a good scanner now that will not shut up. I had to turn some QK's off today as it was information overload. Thats my recommendation. IMHO. FWIW. Your mileage may vary. Greg