RM521F-GL Fails to Connect to n77 / n78 or other 5G Bands

Revision: RM521FGLEAR05A02M4G

I’m having a issue where enable after enabling n77/n78 in both modes along with rest of the bands, my unit is never able to connect to it and the only way it gets any 5G NR(SA) or NSA is if I have n5 or n66 bands enabled. If I disable those 2, it never works in any type of 5G.

On RM521F-GL All 5G (SA + NSA) and LTE bands = Enabled

For Comparison I have included my RM520N-GL results, and noticed that RM521F does not list n77/n78 in the ue_compatibility_band for nr5g_band and nor in policy_band. I’ve run the commands to enable ALL bands on the RM521 but no go.

What could be the issue?, is the firmware from factory on the Quectel modem?

+QNWPREFCFG: “gw_band”,1:2:4:5:8:19
+QNWPREFCFG: “lte_band”,1:2:3:4:5:7:8:12:13:14:18:19:20:25:26:28:29:30:32:34:38:39:40:41:42:43:46:48:66:71
+QNWPREFCFG: “nsa_nr5g_band”,1:2:3:5:7:8:12:20:25:28:38:40:41:48:66:79
+QNWPREFCFG: “nr5g_band”,1:2:3:5:7:8:12:20:25:28:38:40:41:48:66:79 [Note Missing n77/n78]

+QNWPREFCFG: “gw_band”,1:2:4:5:8:19
+QNWPREFCFG: “lte_band”,1:2:3:4:5:7:8:12:13:14:17:18:19:20:25:26:28:29:30:32:34:38:39:40:41:42:43:46:48:66:71
+QNWPREFCFG: “nsa_nr5g_band”,0 (manually locked to 5G SA that is why it displays 0)
+QNWPREFCFG: “nr5g_band”,2:7:8:14:18:20:25:26:28:30:38:40:41:48:66:71:77:78:79 (I have manually selected these bands)

OK AT+QNWPREFCFG=“policy_band”
+QNWPREFCFG: “gw_band”,1:2:4:5:6:8:19
+QNWPREFCFG: “lte_band”,1:2:3:4:5:7:8:12:13:14:17:18:19:20:25:26:28:29:30:32:34:38:39:40:41:42:43:46:48:66:71
+QNWPREFCFG: “nsa_nr5g_band”,1:2:3:5:7:8:12:13:14:18:20:25:28:29:30:38:40:41:48:66:70:71:75:76:77:78:79
+QNWPREFCFG: **“nrdc_nr5g_band”,**1:2:3:5:7:8:12:13:14:18:20:25:28:29:30:38:40:41:48:66:70:71:75:76:79
+QNWPREFCFG: “nr5g_band”,1:2:3:5:7:8:12:13:14:18:20:25:26:28:29:30:38:40:41:48:66:70:71:75:76:79
[Note Missing n77/n78]

OK AT+QNWPREFCFG=“policy_band”
+QNWPREFCFG: “gw_band”,1:2:4:5:6:8:19
+QNWPREFCFG: “lte_band”,1:2:3:4:5:7:8:12:13:14:17:18:19:20:25:26:28:29:30:32:34:38:39:40:41:42:43:46:48:66:71
+QNWPREFCFG: “nsa_nr5g_band”,1:2:3:5:7:8:12:13:14:18:20:25:26:28:29:30:38:40:41:48:66:70:71:75:76:77:78:79
+QNWPREFCFG: “nr5g_band”,1:2:3:5:7:8:12:13:14:18:20:25:26:28:29:30:38:40:41:48:66:70:71:75:76:77:78:79

Troubleshooting, I’ve run the following commands:
AT+QNWPREFCFG=“nr5g_band” = shows n77/n78 as ON
AT+QNWPREFCFG= “rat_acq_order”
AT+QNWCFG=“mode_pref”,NR5G = SA

This is using the exact same sim in my RM521F and RM520N, results are that the RM521F never connects to n77/n78 no matter what I do, my RM520N can lock onto band n77/n78 no problem instantly.

Dear @nosolicit
Please check the combinations after RM520N registered successfully.
I need to confirm if RM521 support the same combinations.

Hello, dear. Can you please send me the combinations?
It can be private message. @silvia

It is sad that Quectel provide absolutely no support.


How do I check all the CA combos supported? You mean all the bands supported once connected? Which I’ve posted above.

RM520 I have locked onto n25+n77

If I disable RM521’s n5 and n66 it immediately fails to connect to any 5G on Telus Canada.

Upon further testing I’ve discovered that the issue only happens with Telus, the modem works on Rogers Canada with NSA and all bands including n77/78 as Rogers currently does not support 5GNR(SA)

However when I insert any Telus sim (I have 5x their SIM cards with the same plan) the RM521 does not pickup any 5G SA besides n5 and n66 combo (n5+n25+n66 / n5+n25 / n66+n25), it keeps hopping bands on LTE without staying connected for more than few minutes.

Once again, no issues on RM520 but issue exists on RM521 only.

Please tell me the commands you want results from so we can address the questions correctly.

I FINALLY got my RM521F-GL working with Simple Admin in a Macuzone Ethernet adapter.

I have never connected to n77, nor n78 with my carrier.
But n71 works ALL the time.

I DELIBERATELY DISABLE n41, as that is ALWAYS slow for me.


+QNWPREFCFG: “nr5g_band”,1:2:3:5:7:8:12:13:14:18:20:25:26:28:29:30:38:40:48:66:70:71:75:76:77:78:79


+QCAINFO: “PCC”,126510,2,“NR5G BAND 71”,168
+QCAINFO: “SCC”,398410,0,“NR5G BAND 25”,2,183,0,-,-
+QCAINFO: “SCC”,389070,3,“NR5G BAND 25”,2,183,0,-,-

T-Mobile USA, BTW…

Dear @nosolicit
Please query AT+QMBNCFG=“list” with RM520N and RM521F.
Which OS did you use?Windows or Linux? It is better to capture a log for analysis.