Uplink, downlink rssi

Hello,
I’m using LoRa network with sx1272 + stm32L0 (node),
and RAK831 (gateway) , also custom network server.

i found that uplink rssi printed in gateway is quite good enough(-32dBm), however, downlink rssi printed in node(stm32L0) is quite bad(-90dBm).

the distance from each other is same, and i use SF 12 & same channel.
the power level gateway use is 23dBm which is the standard of Korea.
I don’t know why this difference happens.

is this problem maybe from end node’s hardware issue or sx1272’s bad sensitivity? or gateway emitting low-quality signal (maybe it’s not).

first try different antenna’s on your endnode… and only test with a greater distance , not a few meters but a few hundred meters.

when i connect both side of antenna with wired attenuator, this problem occurred again. so it’s not the problem of antenna.

anyone have this kinds of problem with sx1272mb2xas?

If both node and gateway are transmitting the same power level and had the same sensitivity then you would expect the RSSIs to be the same.

I have seen a few damaged LoRa devices, but they have always been on the transmit side, in that the power output is extremly low.

Have either unit been operated without an antenna, even for a short time ?

part of my gw config file about tx_lut is below.
my network server gives downlink telling gateway to use 23dBm.
with below config, my gateway could transmit packet with 23dB right?
Or am i do something wrong?

“tx_lut_0”: {
“desc”: “TX gain table, index 0”,
“pa_gain”: 0,
“mix_gain”: 8,
“rf_power”: -6,
“dig_gain”: 0
},
“tx_lut_1”: {
“desc”: “TX gain table, index 1”,
“pa_gain”: 0,
“mix_gain”: 10,
“rf_power”: -3,
“dig_gain”: 0
},
“tx_lut_2”: {
“desc”: “TX gain table, index 2”,
“pa_gain”: 0,
“mix_gain”: 12,
“rf_power”: 0,
“dig_gain”: 0
},
“tx_lut_3”: {
“desc”: “TX gain table, index 3”,
“pa_gain”: 1,
“mix_gain”: 8,
“rf_power”: 3,
“dig_gain”: 0
},
“tx_lut_4”: {
“desc”: “TX gain table, index 4”,
“pa_gain”: 1,
“mix_gain”: 10,
“rf_power”: 6,
“dig_gain”: 0
},
“tx_lut_5”: {
“desc”: “TX gain table, index 5”,
“pa_gain”: 1,
“mix_gain”: 12,
“rf_power”: 10,
“dig_gain”: 0
},
“tx_lut_6”: {
“desc”: “TX gain table, index 6”,
“pa_gain”: 1,
“mix_gain”: 13,
“rf_power”: 11,
“dig_gain”: 0
},
“tx_lut_7”: {
“desc”: “TX gain table, index 7”,
“pa_gain”: 2,
“mix_gain”: 9,
“rf_power”: 12,
“dig_gain”: 0
},
“tx_lut_8”: {
“desc”: “TX gain table, index 8”,
“pa_gain”: 1,
“mix_gain”: 15,
“rf_power”: 13,
“dig_gain”: 0
},
“tx_lut_9”: {
“desc”: “TX gain table, index 9”,
“pa_gain”: 2,
“mix_gain”: 10,
“rf_power”: 14,
“dig_gain”: 0
},
“tx_lut_10”: {
“desc”: “TX gain table, index 10”,
“pa_gain”: 2,
“mix_gain”: 11,
“rf_power”: 16,
“dig_gain”: 0
},
“tx_lut_11”: {
“desc”: “TX gain table, index 11”,
“pa_gain”: 3,
“mix_gain”: 9,
“rf_power”: 20,
“dig_gain”: 0
},
“tx_lut_12”: {
“desc”: “TX gain table, index 12”,
“pa_gain”: 3,
“mix_gain”: 10,
“rf_power”: 23,
“dig_gain”: 0
},
“tx_lut_13”: {
“desc”: “TX gain table, index 13”,
“pa_gain”: 3,
“mix_gain”: 11,
“rf_power”: 25,
“dig_gain”: 0
},
“tx_lut_14”: {
“desc”: “TX gain table, index 14”,
“pa_gain”: 3,
“mix_gain”: 12,
“rf_power”: 26,
“dig_gain”: 0
},
“tx_lut_15”: {
“desc”: “TX gain table, index 15”,
“pa_gain”: 3,
“mix_gain”: 14,
“rf_power”: 27,
“dig_gain”: 0
}

why are you looking at the gateway side and not at the node ?
did you try a different node ?

@LoRaTracker
what do you mean by this??

:rofl:

you really don’t understand ?

From your previous comments you seem to know what an antenna is, so have your operated (or switched on) either unit without an antenna connected ?

I’m quite confused. when i test uplink and downlink of node and gateway, i always operate them with antenna attached. (why should i do without antenna?)

what i mentioned above is wired attenuator which emulate no path loss between node and gateway. when i connect RF sides with wired attenuator, the low RSSI problem on downlink still occurred. (although gateway emits downlink packet with 23dBm).

Because people do, accidently say while they are fiddling around or testing, power a unit on , when there is no antenna on the gateway or node. I have done it.

This can (but not always) damage the device when it attempts to transmit with no antenna. The symptoms of such damage are as mentioned earlier, extremly low power output.

You reported the node displaying -90dBm RSSI from the Gateway packets, suggesting the Gateway has extremly low power output…

what i mentioned above is wired attenuator which emulate no path loss between node and gateway. when i connect RF sides with wired attenuator,

Um, you direct connected the gateway and node RF sides, with what value of attenuator ?

@LoRaTracker
Hi, I tried another end node, however, the problem occurs again.
it seems gateway has some problem.

Below is the log of downlink packet (JOIN_ACCPET). it seems gateway transmit the packet with 23 dBm. I changed gateway board attached to raspberry pi, but same problem occurred.

JSON down: {“txpk”:{“powe”:23,“imme”:false,“tmst”:1128609155,“codr”:“4/5”,“datr”:“SF7BW125”,“freq”:922.5,“modu”:“LORA”,“rfch”:0,“ipol”:true,“size”:17,“data”:“IB1JQeZQg7GSF1647Yi3LDU=”}}
src/jitqueue.c:140:jit_enqueue(): Current concentrator time is 1123764767, pkt_type=0
src/jitqueue.c:117:jit_sort_queue(): sorting queue in ascending order packet timestamp - queue size:1
src/jitqueue.c:119:jit_sort_queue(): sorting queue done - swapped:0
src/jitqueue.c:452:jit_print_queue(): INFO: [jit] queue contains 1 packets:
src/jitqueue.c:453:jit_print_queue(): INFO: [jit] queue contains 0 beacons:
src/jitqueue.c:459:jit_print_queue(): - node[0]: count_us=1128609155 - type=0
src/jitqueue.c:318:jit_enqueue(): enqueued packet with count_us=1128609155 (size=17 bytes, toa=51000 us, type=0)
src/jitqueue.c:433:jit_peek(): peek packet with count_us=1128609155 at index 0
src/jitqueue.c:448:jit_print_queue(): INFO: [jit] queue is empty
src/jitqueue.c:362:jit_dequeue(): dequeued packet with count_us=1128609155 from index 0
INFO: tx_start_delay=1495 (1495.500000) - (1497, bw_delay=1.500000, notch_delay=0.000000)
INFO: Enabling TX notch filter
66.a0.0.43.45.2f.ac.c.0.97.11.10.0.8.0.0.20.1d.49.41.e6.50.83.b1.92.17.5e.b8.ed.88.b7.2c.35.end
INFO: [down] PULL_ACK received in 0 ms
lgw_receive:1155: FIFO content: 1 49 1 5 17
lgw_receive:1174: [2 17]
Note: LoRa packet

What was the answer to the question I asked earlier ?

the attenuator experiment is another thing.

in that experiment, problem still occurs.

attenuator can adjust path loss from -60dBm ~ 0dBm.

when i changing value of attenuator, uplink rssi seems reasonable, however downlkink rssi range is strange. (-130dBm ~ -90dBm)

So you connected the gateway and the node antennas together with a 0dB attenuator in place ?

hmmmmmmm … try reinstalling the gw software , I’ve read somewhere that you seems to have your own loraserver

  • I changed gateway board attached to raspberry pi, but same problem occurred.
  • Hi, I tried another end node, however, the problem occurs again.

strange and not very logical

i mean i changed gateway board with the same new device(RAK831).
i tried reinstalling gw software, however, not effective…

and i think lora server is not the problem as you see my gw transmit log above. it seems gw transmits a packet with no problem. (23dBm, SF7)

Have you ever checked downlink rssi from RAK831?
everyone has experience about uplinks, however, i guess they didn’t check downlinks.

how did you measure that on the RPI ?

why didn’t you try another node and repeat the same experiment ?

Whilst the software might claim to be transmitting 23dBm, you really need to know how much power is actually being sent.

indeed, that’s why I asked ’ how did you measure ’ that