Probably the the easiest way to test if the RSSI your seeing is about right is to use a couple of Arduinos with LoRa modules, one programmed as a transmitter the other as receiver and see what the RSSI is over the same distance when simple 1/4 wave wires are used as antennas.
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Hey guys,
I thought I’d give an update, would love to hear your opinions.
Since my last post here nearly two weeks ago, I had the gateway continuously running and the node was in the same location. The RSSI and SNR was still all over the place, and sometimes I wouldn’t receive any data from the nodes for hours at a time even though they are sending data every 20 minutes.
I tried programming both nodes (Two LHT65 and one MKR WAN 1310) to use AS923 (instead of AU915) and configured the gateway to use AS923 as well and got the exact same results/problems keeping all other variables the same.
I tried different coax, antennas, u.fl → sma, etc. Nothing changed anything. Confirmed good continuity from RAK PCB (pad before u.fl connector) all the way to the N type connector at the antenna. I even changed the Pi 2 to a Pi 3B+ that was being used with the Pi Hat just in case the Pi 2 was having SPI issues.
So I went and bought a RAK WisGate Edge Lite 2 from here.
I’m using it in the exact same location, same coax etc, and the node is in the same spot and I’m consistently getting an RSSI of -88dB every time, and an SNR of either 13.5dB or 13.25dB every time. Everything seems very stable and so far not a single missed RX like I was getting on the RAK2245 for hours at a time.
So I’m going to continue to monitor it. This has been frustrating as I have limited resources and knowledge to test things to try and figure out the issues, but do you think this may indicate that the RAK2245 Pi Hat was somehow at fault?
Never had an issue with the RAK831 and so far the WisGate Edge is performing well. I did originally take extreme care setting up the RAK2245. I wore an anti-static strap, didn’t ever power it up without an antenna connected, so maybe something was wrong out of the box?
Thanks
Thats very suggestive of an RF breakdown of some type, faulty antenna or connector etc. Possibly the Gateway board also.
If the ‘node’ is at 80m then calculations suggest that the RSSI @ 14dBm @ 868 with 2dBi antennas and good line of sight between the Gateway antenna and node antenna should be -51dBm (since the free space loss is -65dBm), which is a long way from the -88dBm you are reporting. However measurements I have done at 434Mhz suggest the RSSI indicated by the SX127x is considerably in error, maybe Gateways are the same.
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It was later moved to ~150m which may help account for some additional loss, also assuming both antenna are vertically aligned, if there is a vertical offset then that may account for some additional loss due to polar plots of both antennas, this would be worse if antennas close - original 50-80m - deminishing in impact as they increasingly move into the far field and relative angle deminishes I guess.
Yes, about 6dBm, so still about 30dBm difference between calculation and indicted. That a lot for a bit of antenna missalignment and would represent a range difference of 30 times …