At the same time, as a comparison, I tried to receive using an RTL2832 SDR receiver (NooElec R820T2) which appeared only a little worse than the RSP1, probably because of the reduced number of bits (8 bits vs 12 bits samples). 

For this test I received the 144.8 MHz with a multi band discone antenna, and the GQRX software on Ubuntu 22.04.