What do you mean you're getting dispatch on a tactical channel?
Outside of Mesa FD and the radio techs, we don't know how they're assigning most of the frequencies yet. If dispatch is on 156.2400, then that is most likely going to be the dispatch frequency. Unless they're testing multiple frequencies to see how their coverage is from different frequencies and/or sites.
154.2800 is the common mutual-aid frequency in the Valley, and that is typically assigned to the channel 4 slot in the VHF radios/VHF deck of the multi-band radios. It will most likely be Mesa FD's VHF channel 4 as well.
The licensed frequencies, in ascending order, are:
151.1675
154.2800 (Mutual-Aid 4)
154.8000
155.6175
156.2400 (Currently Dispatch. The DCS is 411, I can hear it here in Peoria.)
Just because 151.1675 is the lowest frequency, doesn't mean that it's going to be used for dispatch. Phoenix's lowest frequency is 151.3700, and that's channel 10, not channel 1.
We the listeners have to figure out what the programming is going to be, because it's unlikely that anyone with Mesa FD/TOPAZ RWC is going to come on here and give it to us.
John
Peoria