Background and Objectives: Development of techniques and investigation of secondary emission properties of film diamond graphite nanocomposites obtained in different modes of microwave plasma-chemical deposition were performed for sources of electromagnetic radiation of different output power of microwave and subteragetic frequency ranges. Materials and Methods: Production of film nano diamond graphite composites was carried out in a vacuum plant using a microwave ion-plasma source. Precipitation was carried out on polycore substrates using ethanol vapor as a working material at a pressure of 0.05–0.07 Pa. The bias voltages on the substrate holder in plasma chemical deposition processes were 300 V and -300 V. The substrates were heated to 300 ± 10°С in experiments. The study of secondary electron emission (EE) in nanocarbon film structures was performed using the Mira TESCAN scanning electron microscope (SEM). Measurements of the brightness of the obtained images were made at different primary beam energies (10, 5, 1 and 0.65 keV) and different voltages (300, 150, 75, 0 В) on the secondary electron detector grid SEM. Results: A numerical technique has been developed for determining the secondary emission properties of film diamond graphite nanocomposites by the brightness of their images depending on the value of the positive potential on the grid of the scanning electron microscope detector. Using the developed technique, the secondary emission properties of nanocarbon film structures obtained in different modes of microwave plasma-chemical deposition were evaluated. Conclusion: For sample 1: a larger ratio for primary electron energy of 10 keV means that despite the greater depth of electron penetration into the sample, which should lead to a decrease in the secondary electron output, an increase in their concentration as a result of the interaction of the primary beam and the nonelastic electrons with the electron-atomic structure of the nanocarbon material leads to an increase in EE. For sample 2: the decrease in RE yield is definitely due to the lower defect of the film structure and the greater penetration depth of the primary beam electrons, which reduced the probability of reaching the RE surface. For samples 3, 4: brightness values are significantly higher, which confirms the enhancement of the contribution of unelastic electrons from structure defects to the generation of RE at a lower depth from the surface of the film coating.