You want a real-time feel. Premium firmware refreshes the spectrum waterfall every 200ms. Cheap firmware updates once per second, making it impossible to find weak adjacent transponders.
Here lies the biggest trap. The popularity of the Satlink ST5150 has led to a flood of on Amazon, eBay, and AliExpress. These clones look identical but use cheaper chipsets. Their hardware is incompatible with official firmware. satlink st5150 firmware high quality
