It’s going to be rough trying to lock into any of the simulcast P25 sites with the 436HP, or really any scanner outside of the SDS100/200 or Unication G5. The latter scanners are designed to receive CQPSK modulation, which is what the simulcast sites employ. Think of it like trying to get the same signal and decode it from 7-8 different sources at the same time, when those sources are many differing miles apart from you. I had the same issue on Austin’s simulcast and Shreveport/Caddo Parish’s new simulcast until I bought the SDS100, and it receives them flawlessly. However if you are not ready to shell out $700, you can try getting a directional antenna and pointing it at the nearest site to you, or even just moving the scanner to a different spot in the house where it shields some of the farther individual sites better and focuses on the nearest.