LoRa-LoRa - Getting much poorer-than-expected range

End Devices (Nodes) Hardware
1

Hi there!

I’m experimenting with LoRa gear, and am getting range well below what seems to be possible. I’m located in Canada, so I’m using the 915MHz band. My hardware is below:

LoRa Module: https://www.aliexpress.com/item/CDEBYTE-Free-Shipping-915MHz-E19-915MS1W-1W-SX1278-SX1276-chip-long-range-10Km-RF-Wireless-LoRa/32815739318.html

Antenna Adapter (5cm IPEX version): https://www.aliexpress.com/item/5PC-PCI-U-FL-to-SMA-Female-Connector-Antenna-WiFi-1-13-Pigtail-Cable-IPX-to/32955443108.html

Antenna: https://www.mouser.ca/ProductDetail/Linx-Technologies/ANT-916-MHW-SMA-S?qs=sGAEpiMZZMuBTKBKvsBmlOBg0H7cD5uyYD9Wqjm9Eqg%3D

I’m not running any kind of network yet, just sending data directly over LoRa sans-LoRaWAN (using https://github.com/sandeepmistry/arduino-LoRa).

I’m using a spreading factor of 12, a bandwidth of 500khz (with the 500khz optimization registers changed as mentioned in the SX12xx errata sheet), a frequency of 920.0 MHz a coding rate of 4/7, an 8 symbol preamble, and a set tx power of 20 dBm (my understanding is that the module contains an amplifier to raise the transmit power to 30 dBm, is that correct?). With this I’m getting a range of only 350 to 650 meters in a suburban environment, with the transmitting antenna on my house (mounted vertically on the end of a 1 meter wooden stick stuck out my upstairs window) and the receiving antenna in my hand, held up in the air. I should note that this 650 meter range is line-of-sight, straight down a road. Of course, this worsens if I leave the LoS (as expected). Any further than this, and I get garbled packets, or nothing at all.

While I know that some of the advertised ranges for LoRa gear are often not possible in the real world, a few hundred meters seems much worse than what other people seem to be managing, especially considering how high my SF is, and the fact that in Canada we’re allowed much higher transmit powers (1 watt conducted, 4 watts EIRP) than in many other regions.

What am I doing wrong, or what piece of hardware is the limit here? Am I misunderstanding how to set TX power? Is my antenna setup wrong? Or is this just the range I should expect?

Thanks in advance!

2

Please appreciate that this is a forum for the support of TTN compatible devices and software libraries.

Not sure if the non-TTN library you are using supports that device, or indeed if any of the TTN libraires do.

The RX\TX switching it requires is not part of most LoRa device libraries, you could find yourself transmitting with the antenna in effect not connected. One possible cause of extreme short range is a blown transmitter, which can be caused by operating the device with no antenna.

If you want to experiement with LoRa I would start with a standard LoRa module without the added amplifiers.

3

I have set the RXEN/TXEN properly. Would a radio with a failed transmitter still get a few hundred meters? When I first got them, they were set to use the ANT castellation instead of the U.FL connector, I had to move a 0 ohm resistor to switch them. Before that switch, I was able to get only a few meters of range. I have a few more unused modules I could try if faulty hardware is suspected.

4

Possibly, but I cannot be sure as I have no experience of that particular device or the non-TTN library you are using.