How to lock BAND & EARFCN via QXDM?

Tools
1

HI All,
How to lock BAND & EARFCN via QXDM?

1 Like
2

You can’t do it, QXDM is a logging tool.

3

Any other option?
Via NV browser not possible?

4

Probably through OEM Internal App.
Yes but you need to know the right NVM and you need read write access to NV items.
If some one is from QCOM here they and give more info.

5

In my case, I used NV items to lock band with the diagnostic port in phone opening.
Try this: NV settings: NV 65633 – Set LTE Band preference
band 1 0000000000000001
band 3 0000000000000004
band 41 0000010000000000

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65633 LTE Band Preference and EARFCN.

8

Hi all,

Does anyone know if there is an NV setting to band lock NR bands or ARFCN lock for QCOM devices using the QXDM tool?

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Yes, you can do both NR band lock and ARFCN lock on Qualcomm devices via NV items using QXDM/QPST.

1. NR Band Lock
Set NV 65633 for LTE/NR band preferences. It’s a 512-bit bitmask. For NR-only, you’ll usually pair it with NV 946 and NV 2954 to force the UE into NR SA/NSA modes. Bit positions correspond to bands. Example: n78 = bit 78 in the mask.

2. ARFCN Lock
Use NV 6828 and NV 6829 for LTE EARFCN lock. For NR ARFCN, QCOM moved this to NV 70366 + NV 70367 on newer modems like X55/X60/X65. Format is: Channel + Band + PCI. You write the values via QXDM > NV Browser or use EFS Explorer.

Workflow in QXDM:

  1. NV Browser > Read NV 65633 to get current mask
  2. Modify bits for desired NR bands, write back
  3. For ARFCN: Write NV 70366 with target NR-ARFCN, set lock enable in NV 70367
  4. Send NV_MODE_RESET_F or reboot device

NV Calculator Tool
The fastest way is to use an NV calculator so you don’t do hex/bitmask math by hand. Try:

  • RF NV Item Calculator by Sierraware - handles 65633, 946, 2954, and decodes bitmasks for LTE/NR
  • QXDM5 NV Calculator - community tool on GitHub, supports NR bands n1-n261 and spits out the exact hex for NV 65633
  • LTE Band Calculator apps also work if you just need LTE, but make sure it’s updated for NR

Note: Locking can cause the UE to go No Service if the locked ARFCN/band isn’t available. Always back up your QCN first via QPST before writing NVs. And some carriers/OEMs fuse-lock these NVs, so write may fail on retail devices.

Hope that helps. What modem/chipset are you testing on? X55 vs X65 has different NV IDs for NR lock.

10

In that case, I have a question. Someone who apparently works for a carrier wrote that they have an app that gets installed through Recovery and is supposedly signed by the manufacturer or Qualcomm. It supposedly allows forcing specific bands at the kernel level without root. I don’t know if this information is true.

Why do manufacturers defend the ability to force bands so fiercely? I don’t understand it.