Hi all,
I ran some tests on LORA modulation schemes to get the best results I could on a 100mW TX power budget.
I nearly ran out of gas during this latest test, and unfortunately I managed to screw up my data logging, so I don't have RSSI or SNR data, but this map contains all the places I stopped and got a two way signal on my jet ski.
The transmitter was in my hand, the receiver was at pier 50, SF.
DIY half wave dipoles were used, with a center freq of 900MHz with a +/- 100MHz 3db roll off.
I found that quarter wave antennas are no good (see the red markers). The blue markers are today's test, using RFM95's from HopeRF.
To get the very long range, I used the following modulation scheme using the RadioHead library.
RH_RF95::ModemConfig modem_config =
{
/*Reg 0x1D: BW=125kHz, Coding=4/8, Header=explicit*/
(7 << 4) | (4 << 1) | (0),
/*Reg 0x1E: Spread=4096chips/symbol, CRC=enable*/
(12 << 4) | (1 << 2),
/*Reg 0x26: LowDataRate=On, Agc=On*/
(1 << 3) | (1 << 2)
};
RF95.setModemRegisters(&modem_config);
In other news, you can still jet ski if your core body temp is 88F. Little unpleasant though.