The Pi4 suffers from a “bug” which makes the USB throughput very bad. The Airspy Mini falls with airspy_rx from 6 MSps down to 2.1 on an USB 2.0 port and 2.9 on an USB 3.0 port, and rtl_test loses 400 to 15000 samples each read. It requires apt-update, apt-upgrade and CA certificate installation and running rpi-update to get this solved. Might save some time if an updated image (maybe for Pi4 only?) could be made available.
Thanks,
Ben
What exactly do you have to do to solve this? I have had this problem with my RTLSDR as well.
Hi,
Sudo apt update, sudo apt upgrade and finish with sudo rpi-update.
That errorred at first with certificate errors
Sudo apt purge ca-certificates
Sudo apt install ca-certificates
Solved that issue.
Good luck!
Yea. Tried yesterday and had to wait for my brothers new phone to stop downloading apps. As getting timeouts xD
The problem with incorporating this into the image is that rpi-update will place your system in a testing kernel and firmware setup. You are correct that the current kernel they are testing brings a lot of improvements for the raspberry pi, and it is also a big leap for the rest of the distribution (4.19 → 5.4) that requires more testing (for me personally, it raises a rc.local compatability fault that I can’t quite figure out, on something so basic that it should “Just Work”) 
SatNOGS uses pi-gen to generate images the same way raspbian images are generated, so we want to stick to the mainline system as much as possible. I’m not quite sure how image generation would react if rpi-update was attempted in a post-install stage.
With that said, I just double checked and the current image is in fact up to date with upstream (2020-02-13-raspbian-buster). As soon as the 5.4 kernel gets merged in we’ll pick that up for the default image. I couldn’t get a good feel for when that will happen from the thread on the issue but back in April the hope was “a few months”.
cheers!