High-sensitivity observations of PSR J1919+1745 were conducted using the Five-hundred-metre Aperture Spherical Radio Telescope (FAST) at a central frequency of 1 250 MHz, enabling a detailed investigation of its single-pulse behaviour. Our research indicates that this pulsar is a normal pulsar, exhibiting null behaviour, subpulse drifting, and occasional bright pulses. Moreover, we observed that the null events tend to be of short duration, with an estimated overall null fraction of approximately $29.5\pm1.1\% $. Through Sliding Fluctuation Spectrum analysis, the modulation period of subpulse drifting is determined to be $P_3=(6.1 \pm 0.7)P_1$ (where $P_1$ denotes the pulsar rotation period), and a non-drifting behaviour is also observed besides this. Analysis using the Harmonic-Resolved Fourier Spectrum indicates that a combination of amplitude modulation and phase modulation causes the subpulse drifting behaviour of this pulsar. Furthermore, the value $P_2$, derived from phase modulation, is approximately $360^\circ / 21 = 17.1^\circ$. polarisation analysis shows a moderate degree of linear polarisation ($37.22\pm0.59\% $), an S-shaped swing in the polarisation position angle, and an approximate $90^\circ$ orthogonal polarisation jump. The radiation characteristics of PSR J1919+1745 will expand the sample of pulsars with pulse null and subpulse drifting, thus contributing to future systematic studies on the physical origins of pulse null and subpulse drifting phenomena.

The single pulses of PSR J1921+1419 were examined in detail using high-sensitivity observations from the Five-hundred-meter Aperture Spherical radio Telescope (FAST) at a central frequency of 1250 MHz. The high-sensitivity observations indicate that the pulsar exhibits two distinct emission modes, which are classified as strong and weak modes based on the intensity of the single pulses. In our observations, the times spent in both modes are nearly equal, and each is about half of the total observation time. The minimum duration of both modes is $1\,P$ and the maximum duration is $13\,P$, where P is the pulsar spin period. Additionally, the mean intensity of the weak mode is less than half of that of the strong mode. Notably, the switching between these modes demonstrates a clear quasi-periodicity with a modulation period of approximately $10 \pm 2\,P$. An analysis of the polarisation properties of both modes indicates that they originate from the same region within the magnetosphere of the pulsar. Finally, the viewing geometry was analysed based on the kinematical effects.