It would help to know more about your hardware setup, but you could try the following:
- Depending on the Pi you are using, it may have both USB 2.0 and USB 3.0. Alternately, one or more of the ports could be having problems. Depending on a number of factors, swapping the USB port that the SDR dongle is connected to could help.
- If you have other devices on USB on this Pi, make sure they’re all on either USB 2.0 or USB 3.0, not both, since the RPi seems to have trouble with the timing sequence between the two when running ADS-B.
- Your new RPi may generate more RF interference than the previous Pi. If you don’t have one already, try using a USB extension cable to separate the SDR dongle from the Pi. Even 6 inches may do a lot.
- Your new setup may actually be getting better reception than before! Try adjusting gain up or down to optimize it.
Generally, yes, you’ll need a second dongle for UAT-978 reception, but again we’d need to know more about your hardware setup to be certain.