What size or wattage output is the inverter and what type, true sine wave or modified sine wave?
Does the DROP occur ONLY when run on the inverter?
How much power does the laptop draw? It's on the label at the back or on the little box in the AC power cord.
If the laptop or the other equipment gets a poor voltage then odd things can happen.
How have you connected the pieces for the signal transmission? Any questionable connections will result in trouble.
I too use a laptop, not Nobeltec, with a separate GPS, no radar, and the only time we have trouble is when the inverter, a small one, decides enough is enough.