That’s an old post, but just wanted to point out that LoRa point-to-point can be referred to as a digital modulation system, so you don’t necessarily need the hopping frequencies. If you do use the hopping frequencies then it must be 20 minimum, but otherwise, just follow the digital modulation requirements.
So the only restriction is the following for LoRa point to Point:
Digital modulation transmitters
915–928 (915 is not included)
1 W
The radiated peak power spectral density in any 3 kHz must not exceed 25 mW per 3 kHz.
Now I’m not sure how you calculate that it won’t exceed 25mW per 3 kHz, but as a rule, I would say just keep the power low and don’t transmit for too long. But there are no duty cycle restrictions really.
