Measure RF Noise for LoRa networks (900 Mhz)

Hello everyone!

My question is somewhat related to this post on TTN: Is it possible to use a SW defined radio tuned to 868 MHz to detect LoRa Node radio transmissions?

But I am having some troubles with a LoRa deployment using Laird RG1XX Gateways and LCOM antennas (I am using ChirpStack). If anyone here might have some experience tracking down RF noise issues, and could lend me a hand with some advice, I would greatly appreciate it!

Basically, I have 2 locations where antennas are mounted: both are placed on antenna towers between 30 and 40 meters tall (I’m attaching pictures at the end of the post). I am using DR0 for the uplink on the nodes to achieve the longest possible distance, and I am using channels 8 through 15 in the 900 MHz range (that is, frequencies from 903.9 to 905.5 MHz). The nodes are Pycom LoPy4 with 900 MHz antennas.

  1. At location number 1, I have an LCOM 8 dBi omnidirectional antenna at a height of about 32 meters. It is not a densely populated area, mostly agriculture in the surroundings. But lots of bushes and trees that obstruct LOS on occasion. I’ve been able to achieve a good connection with nodes up to 10 km, and sometimes even up to 20-25 km in best conditions.
  2. At location number 2, I have the same setup , but the antenna is mounted slightly higher, at 40 meters. However, my connection with this GW has been very poor . At best, I’ve achieved a 5 km connection with nodes, nothing more. I have attemped many things: replacing the coax cable between GW and antenna, changing the GW, changing the antenna, all have proven to be of no help.

So, I am now thinking it’s related to RF noise around the antenna. I attempted to measure this with an SDR. I climbed the tower at location 2 and connected the SDR to the omnidirectional antenna. I believe I got some interesting results, as lots of short, wideband bursts were observed in the [903.9, 905.5] MHz range (which corresponds to the LoRa uplink channels we are using).

What do you guys think of this? Enough to conclude noise is the issue? Or could it be something faulty in the measurement setup (?) (Which was the SDR connected to the antenna via a 1 meter, RG58 coax cable, and the SDR connected via an OTG cable to an Android Device, using the RF Analyzer app)

Do you have any ideas on how to measure RF noise for LoRa networks more reliably, given the very low noise floor they operate at? Has something similar happened to any of you?

Thank you all in advance.



P.S. Here is a picture of the setup at location 2 (the setup at location 1 is identical).

Location 2