I am monitoring a P25 simulcast system. Using DSD Plus/Fastlane. It seems to be working ok except for some garbled audio. I took a screen shot of the GRAPH displaying while program running. I dont understand this graph. I have everything set to the freq of 853.5125 which is CC for NORTH ZONE. But why is that freq not showing up in MIDDLE of the white hi lighted area in middle of pic? I thought that would be where the main freq would be centered so you can set the bandwidth. I did try to set the correction by typing upper/lower case letter "P" to either raise or lower correction. I am not sure how to set GAIN...its about 49.6 not sure if thats too much or too little. I also have screen shot of whole screen for reference. Using rtl-sdr dongle with vertical 800 mhz antenna. Like I said everything appears to be working except for the occasional garbled audio. The NORTH site towers are all withing 5 to 8 miles from me so I am sure signal is strong enuff.