[Captivate Android Development] AJerman:
Okay, I'm sorry guys, I made a huge mistake and didn't test an actual voice call before posting this guide. I saw it connect to the network, and the data including HSUPA worked, but voice calls have no sound. Not only that, but this DOES only work on 1900 MHz, so if you're in an 850 MHz area, you won't be able to connect to a tower. So for now, this guide is no good. Not all hope is lost though. There are compatible Canadian carriers, and when we get a radio file from them we can try again. For now, don't apply the EU radio to your Captivate or you won't be able to hear anyone in voice calls. Sorry again for not testing better before getting everyone's hopes up. I'll update this thread once I get a Canadian ROM to test.

Well, I've been pretty vocal about this issue, because it's one that really bothered me. Mainly because the Galaxy S supports HSUPA, and really, any new high end phone should. I suspected AT&T was disabling it on the Captivate, likely to save features like that for the iPhone 4, and it looks like that was right.

After a suggestion from trinikartel (thanks twice for good info that helped figure this out!), I flashed the i9000 JP3 modem firmware to the Captivate, and sure enough, the result was:

I've only been an Android owner for less than two weeks, so it took a little while to figure out at first, haha, but the process is very simple:

1. Download an i9000 firmware, I got the JP3 firmware from http://samsung-firmware.webs.com. See my note below

2. Extract the firmware and find the modem firmware tar file. I9000XXJP3.tar for JP3, not to be confused with I9000XXJP3.rar which was the whole archive. If you're not sure, open it up, it should have modem.bin in it.

3. Put your phone into download mode by turning off your phone, plugging it into your computer, waiting for the green battery charging icon to appear, then holding vol+ and vol- at the same time and holding power until the screen goes black, then releasing power ONLY until you get the yellow construction sign that says Downloading...

4. Use odin to flash the modem firmware file. I used all default settings, just click the PHONE button under files and choose the modem firmware tar file, then press start.

It should only take about 10 seconds or so then your phone will reboot and you're done. This is what you should see on odin:

Once it starts up, you can run a speed test to verify that it's working.

NOTES: Of course the standard disclaimer applies, flash at your own risk. Hell, I haven't even had an Android phone for 2 weeks yet and this is my first time flashing, so be careful. It should be a very easy process though.

In regards to step 1 above, I have only tested this with the JP3 modem firmware, however, that's a 2.2 beta or even alpha firmware, so use it at your own risk. Everything seems to work fine with it coupled with my stock JF6 ROM though. I don't see any reason at all why an i9000 2.1 modem firmware wouldn't do the same thing and be more stable though, I just haven't tested it yet. I'm about to test it now, and I'll update this in little while with the results, so if you don't want to use the JP3 firmware, wait a few minutes.