When scanning a trunking system, an Astro system, I get a vice decode fot about 5 seconds, then a constant "hissing" sound, no voice. Doesn't matter if it is the dispatcher or a mobile. Oner or the other talks, 5 seconds then the audio drops and the hissing sound starts. I am using a 396xt, system type is a motorola type II / p25. All other systems decode audio correctly. Setup per RR database, site info exactly what RR says. The systems are not jumping to encryption as I get no beep, sqawks, or other encryption radio sounds, which I get when the FBI comes on the air. Looking for a suggestion or thought here.