In Brazil we use the AU915, which is quite similiar to the US915.
Most recent regulation stands that for bandwiths less than 250kHz the transmision should hop through at least 35 different frequencies and the mean dwell time should be under 400ms within a 14s interval.
For bandwiths greater or equlas to 250kHz it should hop through at least 17 different frequencies and the mean dwell time should be under 400ms within a 7s interval.
Is this the same restriction applied in the USA by FCC15? Or does this 14s (or 7s) window actually defines a duty cycle, also?
Anyway, this clearly limits the SF usage, prohibiting the usage of SF12/BW125 since the 1byte payload message would take about 600ms. Is this correct? @htdvisser did such a great job explaining the duty cycle here (https://www.thethingsnetwork.org/docs/lorawan/duty-cycle.html), I would like to have a clear picture about those other restrictions as well.