Method for operating RF source and related hydrocarbon resource recovery systems

A hydrocarbon resource recovery system comprising:

• a radio frequency (RF) antenna assembly within a wellbore in a subterranean formation for hydrocarbon resource recovery, the RF antenna assembly comprising
• first and second tubular conductors,
• a dielectric isolator between said first and second tubular conductors so that said first and second tubular conductors define a dipole antenna,
• a dielectric coating surrounding said dielectric isolator, and extending along a predetermined portion of said first and second tubular conductors, and
• an RF transmission line comprising an inner conductor and an outer conductor extending within said first tubular conductor;
• and
• an RF source coupled to said RF transmission line and configured to
• during a start-up phase, operate at a first power level to desiccate water adjacent said RF antenna assembly, and
• during a sustainment phase, operate at a second power level less than or equal to the first power level to recover hydrocarbons from the subterranean formation.