The ARK-5 does not have presets. The frequencies values in the ME are used to pre-tune the ARK-5 to those values. If you move the tuning handle, those frequencies are lost.
I set that option as a help for quickly using the ARK-5, specially when a mission starts in the air and you have to land on an airport. So instead of looking for the airport's beacons frequencies, the ARK-5 is already tuned to them. But, if you tune to another frequency, those ME frequencies are lost.