I recommend not trying to program the 436HP manually. Use Sentinel software and make a favorite list for the LAPD. Learn how to Sentinel, and it will make a big difference. I just saw this thread. I am in Cerritos and monitor the LAPD quite often. Have used all the scanners listed below in my signature, and all work well. The 436HP/536HP are my favorites for the LAPD, but all work well. However, depending on your location, you may need a bit more than the stock antenna.
The 436HP is a great scanner. You will like it. There are so many conventional/trunk systems, analog, digital in Los Angeles/Orange County, it will make your head spin. Start with the LAPD, it is easy to program using Sentinel favorite list.
If you have trouble, send me a PM (private mail through RRDB).
Steve AA6IO (amateur radio for 52 years)