Hello Commander!
Indeed, your Support Weapons can support your own and allied bases if no active target is given (It is set to the home base of the weapon.) However, Calibration duration times still apply. That means if a friendly base is alerted by an attack, your support weapon first has to calibrate for supporting that base. Once that is done, fire support is given on any following attack waves, until the base alert/lockdown state is lifted again. Then the support weapon will recalibrate to its home base again.
Btw. If Your Support Weapon is calibrating for a new support target, it can still support its current supported base until the calibration process is finished.
If an active Support target is calibrated, the support weapon will always support this one target until another base is specified, but can fire immediately.
The time depends on the distance and type of Support weapon, but every field of distance adds 40s. (fields diagonally add some odd seconds to that)
I hope that clears up your questions. Setting the active Support for bases can be helpful to protect High Value targets that are the most likely to be attacked first, or often. Simply because your support can act sooner.
