Table 1. Sensitivity Comparison for Constant Sample Size^a.

	S-band		X-band
mode of detection	freq (MHz)	S/N	freq (MHz)	S/N
regular EPR with field modulation	4037	978	9871	1704
regular cavity with VST	4038	714	9871	1250
wire micro strip resonator with VST	3683	237	9829	321

^aThe signal of a dpph powder sample of 4 μL volume was measured under standardized conditions of 100 G scan range, −20 dBm microwave power, no RC-filtering, 120 s acquisition time, and (when applicable) 0.5 G modulation, with the indicated setups. All resulting 1024-point spectra were subjected to 6-point Savitzky–Golay filtering. Signal-to-noise (S/N) values are reported as ratios of the peak-to-peak amplitudes of the signal and the noise in the first-derivative spectrum.