What may be happening is that your scanner is picking up the first control channel it hears and locking onto it for the duration of your listening. To maximize the amount of talkgroups you can hear, you have a couple of options.
1. Put all talkgroups and frequencies into one system. Turn "Multi-site Stationary" on. This will ensure that your scanner samples all three control channels equally when listening.
2. Separate the systems by jurisdiction. Have one system for Richmond, one for Henrico, and one for Chesterfield. Turn Multi-site off, since each system will only have one control channel programmed.
Method 1 makes it a little easier to manage your data on the scanner and helps to reduce the chance of duplicated information, but it also means that you could be listening to more distant sites when you want to hear local traffic. Method 2 is slightly more time-consuming in the programming stage, but basically allows each talkgroup to only be linked to its "home" site in your scanner, eliminating the possibility of missing traffic.
I hope this helps.
