What is Gemini?
Gemini is a dual channel 2.4GHz OR 900MHz system. However, it is currently NOT Dual Band e.g. 2.4GHz and 900MHz simultaneous transmissions.In Gemini Mode, a TX module simultaneously transmits a packet in two frequencies 40MHz apart for 2.4GHz and ~10MHz apart for 900MHz users. The packet separation used is half of the frequency domain selected and will vary a little. A true diversity Receiver is used to receive both packets simultaneously. Transmitting on 2 separate frequencies provides better interference avoidance and/or mitigation, in a similar way DVDA does by sending repeat packets sequentially on different frequencies. This means, the Receiver has an increased chance of receiving the packet. This results in a much higher and stable LQ.
Quelle: https://www.expresslrs.org/software/gemini/