Captivate Modem FAQ's (Updated 4/8)

ls377

Well-known member
Aug 6, 2010
1,462
268
0
Visit site
I’m not a modem expert or anything, but this might be a good reference for those who have signal or battery issues (or just have the itch to flash something). Anyone who has additional info/corrections, post it here or shoot me a PM and I’ll add it to this post.

DISCLAIMER: Me, Android Central, or any member of these forums, are not responsible for what you do to your phone.

What is a modem?

The modem (aka radio) is basically the software portion of the cellular radio in your phone. This has an effect on signal (obviously), and battery life.

Why do I care?

If you’ve never flashed a ROM and don’t plan to, then this probably isn’t something you should worry about. The modem that came with the last OTA update will be the best 99% of the time. However, if your signal diminished with an update, and you’re willing to flash something, then you might be interested in “downgrading” to an older modem.

If you’re using a custom ROM (I9000 based in particular), you may have more to gain. If you use an I9000 based kernel, you will use an I9000 based modem, NOT one made for the Captivate. These work just fine most of the time, but because they aren’t made for your phone or network, you may run into issues.

How do I know what modem I have?

Setting>About Phone>Baseband Version

When should I try a new modem?

If you are perfectly happy with your signal and battery life (yeah, I know there’s only 3 of you, but it has to be said), then don’t worry about it. If it ain’t broke, don’t fix it. If you’re having issues, then maybe it’s time to flash a new modem. Just be warned, some modems will improve your signal, some will do the opposite. If you’re in a low signal area, and have no way of flashing back right away, then wait for a better situation.

Which modem should I use?

There are two basic rules to modems:
1. Use a 2.1 modem with a 2.1 ROM/kernel; Use a 2.2 with 2.2.
2. Use a Captivate modem with a Captivate kernel, I900 with I900 kernel.

Follow those rules, and nothing will blow up.

Here is a list of commonly used and/or current modems. If none of these work for you, then maybe you’re signal just sucks. All files are flashable through clockwork. Everything is there except Captivate 2.1 JH7, JH3,and JF6.


Captivate (2.1) Modems:
UCJH7 - AT&T Captivate from OTA update
UCJH3 - AT&T Captivate
UCJH2 - AT&T Captivate
UCJF6 - AT&T Captivate from stock ROM

If you have the modem file for JH7, JH3,or JF6, please PM me. Maybe I'm just blind, but I can't find them anywhere.

Captivate 2.2 modems:
UCJJ4 - AT&T Captivate
UCJI6 - AT&T Captivate
UCKB1 - AT&T Captivate

Link for Captivate modems: [REF] The modem thread - xda-developers

I9000 2.2 modems:

These all have WCDMA 850/1900 (AT&T 3G) enabled by default. I’m not going to clutter this up with modems without these bands. If you want them, they’re all in the modem thread at XDA.

The modems that contain "UG" (or the Telus modem) prefer 850, while the rest prefer 1900. To use a 1900 modem, you must flash an 850 modem first. See below for the procedure.

I9000DTJP3
I9000AOJP3
I9000BVJP3
I9000UGJK3
I9000UGJK4
T959TLJL3 (Telus Fascinate)
I9000BVJJPD
I9000XXJPY
I9000UGJL2
I9088ZNKP1
I9000ZSJPG
I9000XXJVE
I9000XXJQ1
I9000UGKC1

Link for I9000 modems: [Modems] - Q4 2010 & Q1 2011 (Froyo) - WCDMA 850 enabled - xda-developers

How do I know what to use?

No one modem is better than any other modem. Region, ROM, and other factors can affect which one works best for you. Generally, the more recent the better, but other than that you only have other users’ experiences to go on.

I just flashed a modem, and now I don't have any signal. What do I do?

Most of the I9000 modems default to 1900mhz. You probably live in an 850 area. Easiest way to fix:

1. Start with JK4. It uses 850 as default.
2. Flash a go-between (sort of a middle man). The path seems to depend on the user. I use JK4-KP1-JVE/JQ1, so I would try KP1 here.
3. Boot the phone, and set it down for a few minutes. It has to connect to the 850 band. If it doesn't, make sure you have 850 enabled. If it still doesn't, go back to JK4 and choose a new go-between.
Note: If you live in a 1900 area, there's a good chance you'll lose signal when you go to an 850 area. Have JK4 (and optionally your go-between if you want to use your current modem) ready on your SD card.
4. Once it connects, go back to recovery, choose your modem, and install it.
5. If it boots and you get signal, you're done. Give it a few minutes to lock on. If you DON'T get signal, either choose a new go-between, or add a second go-between (start back at JK4).

Just keep trying different things until it works. If you just can't get it, JK4 will always work with 850. I suggest always having that ready, just in case. (It only takes a minute to change a modem).

What if I need to go back?

Just flash your old modem through clockwork. It's a good idea to keep the file for your old modem on your phone, just in case.

What are your experiences? Have any more questions?
 
Last edited:

stew1411

Well-known member
Jan 24, 2011
179
8
0
Visit site
jl2 or jk4

So im using jk4 right now and in the new di11i update he replaced it with jl2. Is it because its better?

Sent from my SAMSUNG-SGH-I897 using Tapatalk
 

XANAX

Well-known member
Dec 19, 2010
73
8
0
Visit site
From what I understand, modems are only "better" according to area. Different modems work better in different locations. Test out different modems and decide which works better for you.
 

stew1411

Well-known member
Jan 24, 2011
179
8
0
Visit site
From what I understand, modems are only "better" according to area. Different modems work better in different locations. Test out different modems and decide which works better for you.

I like your pic

Sent from my SAMSUNG-SGH-I897 using Tapatalk
 

stew1411

Well-known member
Jan 24, 2011
179
8
0
Visit site
So correct me if im wrong, but do I just flash the new modem to my fone? I read on xda that u need to have a 2.1 rom, flash jh8, then flash 2.2 with a i9000 modem. But since I already have a i9000 rom, can I just flash the modem?

Sent from my SAMSUNG-SGH-I897 using Tapatalk
 

stew1411

Well-known member
Jan 24, 2011
179
8
0
Visit site
At first I was like where the hell did my thread go lol. Then I was like oh it just moved. BTW thanks, that should really help out.
 

lostmind01

Member
Jan 12, 2011
5
0
0
Visit site
i9000 roms such as JK4 unlock HSUPA wich will increase your upload speeds. My experience with JK4 over stock was 1.3mb/s+ compared to .3mb.

Something else i experienced was with both my stock captivate and old i-phone was an echo when i talked to anyone on a CDMA network. That has disappeared with the JK4 modem
 

ls377

Well-known member
Aug 6, 2010
1,462
268
0
Visit site
Didnt see any info for 2.2 with a baseband of I897UCKB1
kernel version reads 2.6.32.9...if that helps

Maybe that's because a certain adviser has neglected updating this thread :-[. I'll update it sometime this weekend.

KB1 is the most recent Captivate modem, so as long as you're on a Cappy kernel, that's your best bet.
 

Trending Posts

Forum statistics

Threads
944,329
Messages
6,922,358
Members
3,159,496
Latest member
caixalegend