Am I correct in assuming that the serial number from the receiver is used only as a product key for the software, the software not actually checking the serial number of the receiver?
If this is the case that would explain why the application picked up the SDR and would also point towards the RadarBox receiver basically being an SDR, albeit with specialized filters and front end.
I dont have RadarBox Hardware. I have only few DVB-T RTL SDR Dongles.
To recreate your situation, I downloaded and installed software AirNav RadarBox 6.01.001 on my Windows Desktop.
I then plugged-in two RTL SDR Dongles, one with antenna, in USB port #1, other without antenna, in USB port #2.
When I started RadarBox software, it found and connected one of the two RTL SDR. As planes were shown in table and map, it was the RTL SDR Dongle with antenna, which was plugged into USB port #1. I repeated start and stop software several times, and it always picked the RTL SDR Dongle plugged into USB port #1.
I then swapped the two RTL SDR Dongles. Now USB port #1 had RTL SDR Dongle without antenna, and USB port #2 had RTL SDR Dongle with antenna.
When I started the software, no planes were shown, hence the RTL SDR Dongle picked was the one without antenna, which was now plugged into USB port #1. I repeated software start several times and it always picked the dongle in the same USB port (port #1).
CONCLUSION: The AirNav RadarBox Software by default always connects to hardware plugged into one particular USB Port.
If that port is the one where you have installed a RTL SDR Dongle, remove the dongle from there, and in that USB port connect Radar Box hardware. Plugin RTL SDR Dongles in some other USB port.