What difference with steadyview x 5.8G and x 5G?

It’s different hardware, the 5G version support X band, also work with 5.8G, but sensitivity may less 1 or 2 db, but the stock 5.8G didnt support 5G(X Band)

5g version support 56 channel and 5,8g only 48 channel.

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5G version frequency table, just delete the Band for 5.8g

what firmware version use 5g version, and what firmware for 5,8 version. Are they using different firmware?

---they are using same firmware, but due to hardware limitation, the 5.8G cant use the X band, because the 4.9-5.9G is way to wide for standard receiver module