This article presents an approach to sensitivity improvement in a detection method based on nuclear quadrupole resonance (NQR); this technique is widely applied in, for example, the detection of explosives. We have an experimental pulsed NQR apparatus equipped with a 250 W pulse power rf amplifier with the working frequency range from 0.5 to approximately 50 MHz. This range can be employed in detecting the isotopes 14 N and 35 Cl. The article will describe certain improvements in the circuitry of the NQR system proposed by the authors and then experimentally verified on the existing system. These modifications lead to an increased signal-to-noise ratio (SNR), thus also increasing the sensitivity of the system during the detection of substances. The main improvements are in the rf blocking circuit, which prevents the power rf pulse from reaching the preamplifier of the receiver. In this position, some impedance transform- ers with switched coils have been tested. The appropriate quenching circuit further reduces the penetration of the excitation pulse to this sensitive preamplifier and thus shortens the recovery time.