Not sure about that. I have a 436 also, and I got my scanners before the SDS ones came out. Then they had some quality issues, so maybe people just held off for awhile. If you still have issues, this RR forum can be a big help with questions. Also, make sure your firmware is up-to-date. Uniden Tech SupportThanks I will look into that. Sounds like everyone has/prefers the 536 here.