We have considered procedure and results of the experimental study for spectral characteristics of self emission from laboratory models of electric thrusters with closed electron drift, with special reference to a thruster with an anode layer (TAL) and stationary plasma thruster (SPT), for a discharge power of 600, 800, and 1000 W, vertical and horizontal polarizations, and various propellants (krypton, xenon). The study allowed us to reveal a number of specific features of radio-frequency emission from thrusters with closed electron drift in the spectral domain. In particular, it was determined that the TAL has a broadband spectrum recorded in the frequency band from 1 to 4 GHz. Vertical polarization dominated in the studied modes, and the level of radio-frequency emission from TAL operating with krypton was 5–10 dB higher than in the case of its operation with xenon. In turn, the SPT has a broadband spectrum recorded in the frequency band from 1 to 3 GHz. Horizontal polarization slightly dominated in the studied modes. For the SPT, the maximum emission level excess in krypton operation compared to xenon was about 10 dB in the frequency range from 1 to 2 GHz for horizontal polarization. The results allow us to solve the problem of quantitative assessment for the effect of emission from thrusters with closed electron drift on the noise immunity of space communication systems.