G0A09:What type of instrument can be used to accurately measure an RF field strength?
Direct answer summary (2023-2027 NCVEC pool)
The official correct answer for G0A09 is A calibrated field strength meter with a calibrated antenna.
The key fact is A calibrated field strength meter with a calibrated antenna. Match that fact to the exact condition in the question; the other choices describe a different rule, band, component, or operating situation.