Recommended US frequencies for LoRa MAC (not LoRaWAN)
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Hi from someone new to LoRa/LoRaWAN, but following the tech for a while and excited about its potential. I've built my first project which reports temp/humidity via LoRa MAC from one house to another about 1/4 mile away using a LoRa dev board, SHT31 sensor, and SSD1306 oled display.
I'm in the US, so am using the unlicensed 915MHz ISM band, which extends from 902 to 928MHz. I'm sticking with spreading factor 7 and coding rate 5/4, which are valid for LoRaWAN, but am not transmitting a LoRaWAN packet. I'm just sending raw data which I listen for and display on the LoRa receiver tuned to the same freqency/SF/CR.
To summarize the US frequency plan for LoRaWAN, there are 8 upstream sub-channels spanning from 902.3 to 914.9MHz, each containing eight 125KHz and one 500KHz channel, and eight 500KHz downstream channels between 923.3 and 927.5MHz. After guard bands, that leaves 8MHz between 915 and 923MHz unused by any defined LoRaWAN channels.
My question is this: if I'm transmitting on LoRa MAC with a signal that is not compliant with LoRaWAN, should I reuse one of the 125KHz upstream LoRaWAN channels? Or is there a recommended LoRa MAC channel plan somewhere that uses frequencies not in the LoRaWAN channel plan? For instance, should I stick with the 200kHz spacing continuing up from 915.1 through 922.9MHz and just pick a quiet frequency?
I know it's an unlicensed band, and I expect I'm legally fine to transmit anywhere within it as long as I stick to 30mW or less, but would like to play nice with what's out ther eand what's to come. I'm also rural enough that I don't expect my signal would clobber anyone else anyway.
Expert advice from someone familiar with channel plans and US regulations welcome. Thanks much!