I’ve been messing around with my configuration. I have a device approximately 3KM away from my gateway I want to connect to and sometimes I can see a join request but very rarely can I get any sort of reliable connection, usually not at all. I ended up changing the antenna you see in the picture (5.8dBi) above to a 3dBi antenna I got from an Australian IoT store, you can see the product here.
I know this is all mostly irrelevant but I wanted to ask: I have a device about 80 meters away from the antenna, an LHT65 (Dragino) and it’s clear line of sight to the antenna, and it works fine but the RSSI is -72dBm and the SNR is 13.2dB.
I wanted to ask if these would appear to be normal levels for a device so close to the gateway? Especially the RSSI. I’m just trying to work out if I could have an issue with the pathway from the RAK2245 to the antenna that could be causing me issues with my attempts of connecting to the device 3KM away I mentioned above. I am using cheap coaxial cable and a u.fl adapter I had laying around so I plan on replacing it.
At the moment I’m leaning more towards it being an issue with a hill between the two devices (3KM) but I’m not sure.
Edit: I found some graphs online that seem to suggest that -72dBm is an appropriate measurement considering the distance of the LHT65 from the antenna so that is good.
Assuming a node with 14dBm output power into a 0dBi antenna the signal should be about -50dBm. The missing 22dBm can be caused by: polarization, disturbed Fresnel Zone, antenna of the node, measurement uncertainty of RSSI, TXpower reduced by ADR …
There are many factors that can and will influence the propagation. If you want to do a real measurement you have to go to an EMC-laboratory with a fully anechoic chamber or a free-space antenna-field.
Additionally it could make sense to look at the radiation diagram of the antenna.
Devices do not connect to gateways - devices transmit, gateways hear, the network server issues credentials. A universal misunderstood concept. The key takeaway in this situation is that you could have another gateway somewhere else to listen in.
The Elevation Map line is in red - that should tell you far more than anything else we can say so as mentioned above, you should also read up on Fresnel Zone.
You talk about 3km and a hill, this should already ring a bell, what other cutter do you have? Buildings, trees or?
Your evaluation map is 1.88km, that is just about level with a hill, again what clutter are there besides the hill? All obstacles - clutter do attenuate, block RF, some more some less.
Yes I’m aware you’re communicating with the network server and not the gateway itself, I was just trying to describe my issue.
I found the elevation map data after making my post so yes I agree, that is probably part of the problem.
I’m just after any advice and information I can get. I’ll research the Fresnel Zone, thanks.
There’s not much between the two points, some residential buildings spread out on 10 to 50 acre blocks of land and not too many trees, but there’s certainly some the signal would have to pass though.
I obviously can’t really show the area in depth without giving out my location which I won’t do but from what I’ve read up today I don’t believe there’s anything wrong with the gateway setup, it’s most likely going to be a combination of the land and obstacles.
I think I’ll try get the antenna a bit higher up and keep trying.
So when I first made the post I had an RSSI of -72dBm and an SNR of 13.2dB. This would have been approximately 50 to 80 meters from the gateway antenna LOS.
I have since moved it probably another 80 meters. Say approximately 150 meters LOS from the antenna. The RSSI is now -84dBm and the SNR is 10.5dB.
I’ll try and get some more accurate measurements and also some readings from a further distance and post them here.
If you double the distance, the RSSI should decrease by 6dB (in theory). But still there are more than 20dB missing. Try to turn the node by 90 degrees and observe what happens to RSSI.
I’ll get some more accurate measurements and post them here.
Could a faulty coax link between the antenna and the gateway cause unexpected drops in RSSI vs distance? Just out of curiosity. Poor connection in one of the joins, moisture, etc.
I’m logging the data to my database and I took a screenshot of it to post here. It does seem to move around a lot, before and after I relocated it:
It has always been clear line of sight. The antenna is above the peak of the shed roof as seen in my previous picture. The node this data is coming from has always been about 1 meter off the ground, but clear LOS.
I would not care about ±3dB of RSSI or SNR. My gateway receives a Node that is transmitting a 19 bytes message every 12 seconds. It seems to be in a fixed position but RSSI (-116 dBm) and SNR (-3dB) are changing by ±3dB every reception.
Sometimes the SNR is even worse - the message can not be received (to much “noise”).
I don’t know where and how far away the node is situated, if I knew the owner I would tell him about FUP. On the other hand this is an interesting beacon.
If you had 3 gateways and could log a few 1000’s of it’s messages, you can get fairly close on the location of it. (but you will use RSSI for location, you could be out a few 100m thought)
So I’m currently at work but noticed I’ve lost the node, no RX at all for the last 2 hours.
This actually happened a couple days ago briefly.
I still suspect something isn’t right… I have an MKR WAN 1310 I’ve also had intermittent issues with. The LHT65 is brand new but I can’t rule it out either.
The last RSSI/SNR was -85dBm/8.5dB.
I suppose it could also be interference from something… very odd. I wish I had the equipment and know how to work this out.
I’m going to order new, quality coax and adapters I think.
Edit: Getting received data sporadically every couple of hours instead of every 20 minutes all day so far.
If problem with multiple nodes suspicion turns to the gw(*) and any associated internet backhaul. What do the gw logs show wrt status/traffic etc. what does the TTN console tell you wrt gw connectivity……do the node ‘outages’ match to gw issues? Where in the world are you, what backhaul are you using?
Appreciate that, but the more detail and surrounding info we get the better the prospect for the forum volunteers helping find a resolution or providing effective advice. We don’t need your burglar alarm code
(*) if gw not your own can you contact gw owner to ask them to share appropriate info. Is there a local TTN community, are you/gw owners members? Perhaps others in the area/community see similar drop outs….may help track down cause….gw, backhaul, interferers….
I’m not sure how to check the gateway logs on the Raspberry Pi with the RAK2245. I’ll definitely investigate though.
I previously had a RAK831 running on AS923 and never had an issue like this, with the LHT65 in the same location. The gateway I’m using now is a new Raspberry Pi + RAK2245 (AU915) Pi Hat and new coax cables.
The Pi is physically connected via Ethernet back into my network, and I have an ADSL2+ back-haul running at about 22Mbps downstream and 1Mbps upstream. The line has 100% uptime and runs no CRC/FEC errors at all.
There’s no local TTN community, I’m in a rural location and it’s a small town, so I’m kind of on my own with this one.
But I’ll try find some logs tonight as soon as I get home. Thanks.
Last RX was 4 hours ago at the moment. Should be every 20 minutes.
