[greggold]

I asked on the ELRS discord, and there is apparently an 'AU915' mode, which may restrict it to legal frequencies for us

great clarification .... In gemini if you choose 2.4 Ghz band for both tx emissions, the difference between them is 40 mhz, so if that difference is the same for 915 band, then choosing AU915 would mean 915 mhz for one tx emission and 955 for the other - so maybe AU915 would mean 915 and 928.   Bardwell (above link) has made the point on 868/915 mhz band (now referred to as low band in discussion of gemini x) that it has major benefits (greater range, better penetration of obstacles) at very low cost. Its drawbacks include bigger antennas for rxs and txs, and increased latency. However the latency issue may only affect drone racers, who reduce the latency by several millisec by choosing 2.4Ghz over 915mhz. Bardwell says this difference in latency is undetectable by normal rc flyers, and it seems to me to be beyond human physiology to detect such a tiny difference in response time. But top drone racers do amazing feats so maybe they can tell the difference.

I flew on 915mhz with my frsky tx and a module for a while before elrs arrived, and like others found that it completely ended the prcac glitch/interference problems. I will consider it now because my favorite bnf drone - geprc tern - is sold in 2 versions, 2.4 and 900 mhz. When I want to try long range over a river it seems like a good choice.