How do I go back and change the System from conventional to P25 One Frequency?
No such thing as a one frequency
P25 system. A P25 (trunk system) requires at least two frequencies, one is a control channel the other for voice traffic.
FYI: You can use P25 digital audio (CAI) on conventional (channels) frequencies (FM, NFM, etc..). Where I live the Park Service has multiple conventional frequencies and use P25 for the audio.
To add the three frequencies to an existing Favorites List:
Add a
System (give it a name) set the System Type as
Conventional, assign a Quick Key.
Select the new System (in the left panel). See Departments on the right. Click on the Plus, enter a Department name and a Quick Key.
Click on the new Department on the left panel. Add a Channel (enter a channel name) set the Modulation (FM, NFM, etc..) enter the Conventional Frequency, enter the Audio Option (you can leave it at Auto or enter Digital and NAC, make any entries you want in the additional fields.
You are done with that frequency. Click on the Plus key to enter the next frequency (channel).