Long range settings

[m15code]

I tried to make settings for long-range, but with bw 31.25kHz, the message wasn't received. Also, I observed that with sf12 bw500kHz works to send and receive packet of data but with small length. If someone knows what settings works for 3km range. Another problem that I observed, if I try to use arduino with radiohead library, at RX the RSSI is around -18dB, and with cpy, is around -50dB at 50cm distance between rx and tx. Sf11 and Sf12 works with 128 preamble length, but the rx lose packets. I have adafruit feather m0 rfm9x lora, and I use 433 MHz.

[jerryneedell]

This is likely related to #70.