Losing the control channel is a classic sign of simulcast issues. You can have a very strong signal, but the scanner is unable to decode it. Above the system quick keys, you should see the control channel frequency when talkgroups are not being received. If it displays NFM, you have lost the control channel. Assuming that the scanner receives properly at times, if you lose the control channel, it is due either to a weak signal or simulcast problems. If you see NFM, the control channel is not detected. With simulcast systems, you have the same control channel data arriving at different times from multiple towers in the site. The scanner is then unable to decode the information. Only the Uniden SDS100/SDS200 scanners and Unication G4 and G5 pagers were designed to deal with simulcast.