Richmond area Federal Interoperability Communications System
My best guesses with comments..The two frequencies, 150.2375 mhz. and 150.3500 mhz. are related but do not simulcast the others' transmissions. Numerous varied NACs are used with two of most currently active being 214 and 230 but will change as new users transmit. As posted all transmissions are P25 encrypted. These two transmissions will provide wide area coverage centered on Richmond. A number of federal users now share previously dedicated single user only frequencies. This practice allows for more remote site simulcasting which results in a wider geographical area coverage. In this case these are two separate separate standalone alone transmissions interfaced to the system and do not appear to be repeaters. Possibly a dedicated T1 line with a system controller is providing the T/R and audio interfaces. Two frequencies are used because first it provides redundancy if one fails and maybe secondly if the traffic volume on one transmitter reaches a threshold level the requesting user's comms are redirected to the other transmitter. To the user the comms are seamless.
If a federal user's radio can access one of the system's interlinked antenna locations he/she can simulcast throughout the total geographical coverage area of the interlinked system. For example, an ICE unit in Washington can have comms with an ATF user in the Richmond area or wherever the system is interlinked geographically. In NOVA I've heard these type of multi-frequency system comms typically in the 163-170 mhz. range. Again, you are not hearing just two federal users in Richmond. The comms heard may represent different federal agency users from different geographical locations possibly in the VA/MD/DC areas or other selected geographical interlinked locations. That's why the comm activity appears to be frequent at times.
If not already active I suspect Tidewater and western Va. in time will have comparable systems.
