The noise amplification regime in a plasma maser with inverse geometry was obtained experimentally for the first time. It is shown that the introduction of a microwave absorber transfers the maser operating mode from the oscillator to the amplifier. In both modes, the tuning of the radiation frequency has been shown when the plasma density changes. This work is a step in the implementation of a plasma relativistic noise amplifier with a short pulse REB. © 2019 Federal Informational-Analytical Center of the Defense Industry. All rights reserved.