[YotaPhone] TheArt.:
UNLOCK LTE BAND B20 - 800Mhz and B38

I will translate here the work of three 4pda users who must be thanked a lot for their work! unkernet, ssho and BoyNG. Thank also to mamant1988 who put everything together.

The original 4pda guide can be found here (in russian): http://4pda.ru/forum/index.php?showtopic=797643&view=findpost&p=59716629

UNLOCK B20 LTE BAND ON YD206​

Starting point is a rooted YD206 with latest RU 134 firmware, TWRP and ADB-USB-debug enabled. Do this procedure carefully and write down all the modifications and default values. The changes are performed on NVRAM level, so flashing firmwares will not affect them. Flashing firmwares will, however, affect modified baseband, as any other "radio" part as usual.

Download here the .zip archive which contains what is needed for this guide, including some screenshots of how things should be displayed.

Download the modified baseband RU-CN here and put it into the internal memory of the phone: it will be flashed in the end.

Install QPST and QXDM Qualcomm programs on Windows, they are in the above archive.

Enable the installation of unsigned drivers in Windows (like this). This is needed to install drivers for the diagnostical port later on.

Download Terminal Emulator from Play Store.

In the Terminal, write the following to get root access:

su

then:

setprop sys.usb.config diag,adb

Connect the phone via USB to the PC, in the Device Manager it should pop up as "Android Device" or similar, without a specific driver.

Right click on it and perform these actions: update drivers, search on this computer, choose driver from already installed drivers, show all devices, next, install from disk, there point to the .inf file corresponding to your system (32bit -> x86, 64bit -> x64) found in \YotaLTE\Modified HTCDiagDriver\Win x64HtcUsbMdmV64.inf (for 64bit).

After installation, go to properties of this new driver HTC USB Modem and check the number of the port displayed there, COM3 or COM4, for example.

Lower the 38400 value which you find there, click OK.

Execute as an admin C:\Program Files (x86)\Qualcomm\QPST\bin\QPSTConfig.exe.

Choose the second section Ports, then "Add new port".

In the field Port put the one which was displayed in the modem section, COM3 for example.

In Port Label field write "Yota" or whatever, and then OK.

In the first section Active Phones the smartphone should be displayed.

KEEP QPSTConfig.exe PROGRAM OPENED.

Also, start C:\Program Files (x86)\Qualcomm\QXDM\Bin\QXDM.exe using admin privileges

Here, click Option, then Communications.

In the Target Port choose the same port as before, then OK.

Click View, New, Common, NV Browser. In the Category Filter choose LTE.

Choose 06828 LTE BC Config and then press "read".

Correct the number you see, for example 1099511627781 in 1099512152069 for B20 and click Write to save.

Close all the programs, and reboot the phone directly into TWRP (VOL UP + POWER), here find the update_S01_003_4240_RU1_M05_patched.zip baseband and flash it.

At this point it is advised to clean dalvik cache and cache with TWRP.

Done! Reboot.

If it is not working, reset everything by flashing stock baseband, putting back the values changed above and start again. It is not necessary to flash the modified RU-CN baseband, if with the CN one the phone is performing at 100%. I suggest to flash to see the differences. By the way, remember to unlock one band at a time.

To unlock B38 band (there is lack of information about YD206 already having it or not) the number is 1236951105541. For example, if the initial number found in LTE config was: 1236950581253, it means that the bands LTE B1/B3/B38/B41 were active. To verify by yourself download LTE Band Calculator.

Some attempts have been made also to unlock B7 band, but without success for now. It seems that the baseband crashes after a second when triying to connect to that LTE band. Further research needed!