Using LoRa (forget LoRaWAN for the moment), if I want to increase my range I can:
Given that 2) and 3) increase the duration of the transmission, what is the most power efficient way of increasing range?
according to shannon law, 1) 2) 3) almost the same, 1)is most expensive.
As suggested in theory they should be the same, in practice the amount of RF power actually output is not linear to the amount of consumed current for typical devices. Above 10dBm a typical RFM98 will consume 5mA per dBm, but at 2dBm its up to 16mA per dBm.
Then there are practicalities, using a bandwidth below 62.5Khz can be problematic, transmitter and receiver might be outside of the capture range due to natural manufacturing tolerances in the timing crystals used.
Increasing antenna height is often the easiest way of increasing range.
Great point about the TX power being more efficient at higher levels. I’ve also kept BW at or above 62.5khz for the reasons mentioned. So is there any reason you’d choose 62.5khz SF7 over 125khz SF8 or vice versa?
Tried with a TCXO version of the RFM95W (RFM95WT), it also doesn’t work 100% down to 62.5 kHz especially if data is longer with high SF.
Well, the TCO might help the temperature drift, but it does not necessarily improve the accuracy of the tx frequency in relation to the rx frequency. Its not difficult to add a calibration offset in any case.
I have not had a a problem myself with long packets (7 secs or more) at BW62500, SF12
Getting packet failures with longer packets can happen if the optimisation bit is not set correctly.
For range, anyone try yagi antennas? (At node end.)
Yes, and for point to point links they give the range improvments you would expect, around 3 times further for a 10dB yagi, 7 elements maybe.
But yagis are highly directional and whilst ideal for long range point to point use are not very suitable for TTN style applications.
If your system uses a SX130X based gateway, you’d better use 125 kHz as 8 of the 9 SX130X channels only support 125 kHz bandwidth.
I agree with @BoRRoZ : provided you are already using the maximum tx-power out of your node (and maybe even running in the the regulatory power limit) and the maximum SF, then it pays off to use a good antenna, maybe directional, and choose the best antenna position.
Remember that a good antenna helps you both in transmitting and receiving, whereas increasing TX-power only helps you in transmitting!