[Oppo A37 Questions & Answers] alular:
Hi, everyone. :)

It might be a long post, so for saving your time, I will put my key question here. :)

1. If a device which only supporting certain carrier's 4G could work properly for SMS and phone call?

2. Is it possible to directly use the official rom of A37m (MTK6750) on F1S (MTK6750)?

3. How I extract only the baseband from the official rom of A37m, which is ColorOS and put it into an F1S?

I'll put the full story here.

Few days ago, a friend from China come to visit me. And he want to purchase a mobile as the camera of his one is so bad. According to his quest(1. Chinese brand; 2. Good camera; 3. Low price; 4. Support China Telecom), I choosed OPPO F1S for him. It was working well here in Dubai.

The problem starts when he's back to China. :( He contact me for that the 4G SIM card form China Telecom was not working with the mobile (showed no signal). To solve it I did all these below:

1. I checked again that if F1S supporting China Telecom's 4G(which seems to be at frequecies Band 3 1800 and Band 41 TD2500). And both the offical website data and result from FrequecyCheck.com approved it.

Here's the result:

2. As from 1 it seems that the problem wasn't from the device, I requested my friend to visit China Telecom office to change another SIM. And he did it, problem still remains :confused:;

3. I requested my friend to borrow a mobile from someone and put his SIM in to see if there is single, which he did it. He borrowed an iPhone SE (A1723), and the SIM card was working well in it. As there was no iPhone SE on FrequecyCheck.com, I checked iPhone 6S (A1700), which is of the same baseband. The result is here:

Wait, for LTE the compatibility is same with F1S, but it also support CDMA at BC0(800) and BC6(2Ghz). :mad:

But why I need CDMA(3G, as I thick) if have LTE(4G, as I thick)? And after some search on the Internet I found articles saying that without VoLte the device had to access 3G or 2G to use SMS and phone call. :confused:

I was upset but the official web site of R9m(which is the Chinese local version of F1S, as some website says, and according to another friend in China who is using R9m, her mobile works well with the 4G from China Telecom) gave me some hope:

Then I started to have a stupid idea that F1S may also support CDMA band, but somehow it's locked.

4. I started asking my friend to try those "secret code" like *#*#4636#*#* and *#800#* to enter hidden menu while I gave him advise via video chat. I did find a Band Mode menu there (which shows EURO band, AUS1 band and AUS2 band, neither makes any difference) and a baseband choose menu (have Band 0 to Band 41 and so on, and some are selected, but those which are not selected can not be selected). After many hours of trying, I gave it up. :crying:

5. I started to think about that maybe I have to get a baseband from another OPPO device, which supports CDMA and put it into F1S (now with a baseband MOLY.LR11.W1539.MD.MP.V20.3.P30). The R9m was my first choice but then I found A37m, which is with a same MTK6750 CPU. Here is the offical website data and result from FrequecyCheck.com(sorry for the Chinese):

But then after hours of search on the web, I found there was no ready-made baseband pack of A37m on it. I tried to download an official ROM of A37m from OPPO website and extract it, trying to find a file named modem.img or radio.img and here's what I got:

Can't recognize which file is baseband related.

Then I also download an official ROM of F1S (named A1601) and extract it to see if I can find which one is baseband pack by comparing both ROMs:

But with my ultra-limited knowledge I think I got no way to recognize it as well. :(

Thus, with my biggest and last hope, I'm here, seeking for any help from anyone. :)

Again, I think I need to find out:

1. If a device which only supporting certain carrier's 4G could work properly for SMS and phone call?

2. Is it possible to directly use the official rom of A37m (MTK6750) on F1S (MTK6750)?

3. How I extract only the baseband from the official rom of A37m, which is ColorOS and put it into an F1S?

Please help me. Any advises would be appreciate. :)

Thank you.