Changes for page Notes for ChirpStack
Last modified by Edwin Chen on 2025/01/30 09:53
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... ... @@ -909,5 +909,31 @@ 909 909 ((( 910 910 Under normal circumstances, users need to change the APPKEY to solve this problem. 911 911 912 - 912 + 913 +== 11.2 The node is very close to the gateway, but the signal is poor == 914 + 915 +If you are using US915 or AU915, you found the frequency points of different subband ranges in your uplink 916 + 917 +Like that:Both 905.1Mhz and 902.3Mhz appear on uplink 918 + But they belong to Subband1 and Subband2 of US915 respectively 919 + 920 +Cause: The server and the gateway use different frequency bands (the server uses Subband1, and the gateway uses Subband2) 921 + 922 + In server side, it shows the frequency is 905.1Mhz, which is sub-band2. But the RSSI is very low, Because this is not a signal in 905.1Mhz, it is on 902.3Mhz, the signal is too strong and appear a noise in 905.1Mhz. 923 + 924 +How to check the frequency band used by the server: 925 + 926 +You can view the information sent by the server: ch_mask in Unconfirmdedatadown 927 + 928 +[[image:image-20230821113255-1.png]] 929 + 930 +According to lorawan's protocol, your first ch_mask is 7 for ChMaskCntl = 7 then 125 kHz channels are disabled. Simultaneously the channels 64 to 71 are set according to the ChMask bit mask. 931 + 932 +[[image:image-20230821113539-2.png]] 933 + 934 +In the second message, the channel 0~~7 is true, which means that your server is using subband2. 935 + 936 +[[image:image-20230821113618-3.png]] 937 + 938 +Note:lorawan's protocol link——[[LoRaWAN® Regional Parameters v1.0.3revA (lora-alliance.org)>>url:https://resources.lora-alliance.org/document/lorawan-regional-parameters-v1-0-3reva]] 913 913 )))
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