I have been using a Regency 10 channel crystal scanner for several months for my Centre Ala Police and FD feed. It has reasonable selectivity and worked flawlessly until about 3 weeks ago. Suddenly I am plagued with dreadful interference from my KB4UPI 10 meter beacon transmitter running 5 watts located only 60 feet away. Thinking the 10 meter tx was at fault I checked the signal and it was clean. I checked the antenna connections. I checked every audio connection and plug on the scanner, the SignaLink interface, and the computer. I even soldered some connections that I hurriedly twisted and taped up. Nothing helped, so I resorted to my old iron clad rule, and that rule is "change something". I pressed, released, and reselected one of the channel selector buttons on the front of the radio. This cleaned the switch, Lo and behold, the interference and noise went away and has not been heard since. A dirty switch and RF is not a good combination. The moral of the story if you are using a crystal radio is "work the switches weekly to keep them clean".