Use your 651 to listen to encrypted noise. The 396xt is set up to not only mute, but ignore encrypted signals.
Strangely Uniden then came out with the x36 radios that continue to ignore and mute phase 1 encrypted signals, but blast away on the phase 2 encrypted transmissions.
Mark
WS1095/536/436/996P2/HP1e/HP2e/996XT/325P2/396XT/PRO668/PSR800/PRO652