Is the STM32WL5JC has TCXO oscillator for the LoRa transceiver? What is ppm frequency accuracy?
I would like to send 20 bytes to maximum distance using maximum spread factor, SF12. On air time is about 1.2 seconds. From reading, standard bandwidth seems 125 kHz. I may have to reduce bandwidth to, says 30 kHz, to increase receiver sensitivity.
1. How is the oscillator frequency tolerance between two boards? Presumably, I should not reduce bandwidth too narrow toward the freq tolerance limit. Any idea on a safe value? Twice crystal ppm plus some margin, plus some for sensor at motion (says 3 to 5 miles per hour)?
2. The packet tx time is "long" at 1.2 seconds. Will the oscillator drift within the tx time become significant? Seem read 'automatic frequency correction/tracking/compensation' some where? Does this chip has such facility? Is it turn on "low data rate optimization"? I can heat up the AC powered base station to, says, constant 40 Celcuis for low drift.
3. Will distance of 2 km (1.5 miles) sounds possible? 868MHz, Europe specification is 12 dBm. Residential area. House are brick (not wood, not concrete, no steel bar). It rains 150 days per years and brick can be wet and attenuate signal. Antenna height of sensor is low. Base ant is ground floor, indoor at window, or can be outdoor if needed.
4. Some reading say LoRa degrade a bit when the sensor is moving. At tx time of 1.2 seconds, SF12 and low bandwidth (30 kHz), what speed is ok?
TIA
