I’ve just added a small amplifier to my setup, very inexpensive, and doubled the received messages as well as extended the range.
0.01-4GHZ 21DB Wideband LNA Amplifier Module High Gain Low Noise Amplifier HAM Radio RTL SDR LNA Amplifier Broadband https://www.amazon.co.uk/dp/B076ZDBGJZ/ref=cm_sw_r_cp_tai_5Ra8Cb9AZ5PDJ
Used a SMA coupler to connect it directly to the SDR, and 5v power from the Pi GPIO header.
A very effective addition to my setup. I’ve ordered more for my other stations too.