Help Low signal strength when using an unlocked international on the AT&T network?

[jungleexplorer]

I know this is a phone support issue, but there are almost no users on this forum for my particular phone model and I have gotten no response to any question I post under my phone model, so it does no good to post over there. I am hoping maybe someone in this general forum might be able to help me. Besides, the problem here is not unique to my phone model. Many other people with different phone models have the same problem.

I am with AT&T. For the last three years I have used an Sony Xperia V on the AT&T network without problems. I have gotten great signal strength anywhere I go with the Xperia V. The GPS antenna gave out on it and I went looking for a new Xperia. I landed on the Z3 and order the international model (D6603). I got it and got a new AT&T Nano sims for it down at my local AT&T store and the phone worked right away. I downloaded the AT&T APN settings and got the data to work. The Z3 works and can make calls, text and it gets data service (only H+ though). I absolutely love my new Xperia Z3 (functionality wise). The only problem is that I have almost no signal.

Now, I know that there is good signal strength where I am at because I have used my Xperia V in this area for 3 years and I have always had full bars of signal in my area. My Z3 only gets 1 to 2 bars, and sometimes none. My wife has a Galaxy S4 (with AT&T) and gets full signal in out home. We were on the road yesterday and I was on the phone with my mother and the call dropped because of no signal. My phone had the little red X on the signal bar. I looked my wife's S4 phone to see if she had signal and she had full signal strength. For about 20 miles (in an area I know there is good signal) the Z3 could not pick up any signal at all, but my wife's S4 had full signal strength and was doing facebook the whole time.

I have done many searches about this and have found many other people that have the same problem on many different models of unlocked phones when it comes to at&t. I am just wondering if anyone has found a fix?

 

[Hadron]

No experience of this myself (I've used ATT when visiting the States, but then I'm an international roamer so things may be different). That handset should be OK for frequency bands (3G and most ATT LTE bands), so it has to be something to do with AT&T's systems. The early posts of this xda thread refer to some off shennanigans of registering IMEIs with ATT (??? - that's not standard for GSM networks), but it's not clear that this is still relevant nor that this is the same problem.

 

[jungleexplorer]

Okay. So I think I found the problem. The problem is with the 3G and 4G bands. I downloaded the LTE Discovery app and ran it on my Z3. Here is a screen shot.

Then I took the sims card out of my wife's S4 and put it in my old Xperia V phone. Sure enough, just like always, it got full signal. So I ran the LTE discovery app on it. Here is the screen shot from the V.

So we can see that the reason the V is getting full signal is that it is operating on HSPA+ and the Z3 is operatiing on 4G LTE. Now I don't now why this is happening. Perhaps that is a 3G tower that is closer to me, or the 3G band travels farther then the 4G. I don't know anything about tower strength and technology. Anyone else have some ideas?

 

[mikedt]

Looks like the signal strength is definitely right down. Could be the phone has a bad antenna, or other hardware problem with the radio. Worth see about getting it replaced or repaired under warranty? I believe this phone should work with AT&T no poblem.

 

[zuben el genub]

I've seen that on an Oppo Find7 on Tmobile. What bands are available for you? The Oppo barely picked up band 4.

I have the same app. Now I have a Moto X pure. TMO keeps changing the tower - at least the direction arrow keeps moving.
I will get about the same on Band 4, but will get more on a Band 12 area if I'm in one. If I switch the phone over, then HSPA+ or 4G is really strong. The X Pure does do voice calling on band 12. Didn't know that. It was one of the unlocked group of phones including the Nexus line.

Why not try a phone forum? Usually everyone over there is posting speeds all the time.

 

[Slug]

So we can see that the reason the V is getting full signal is that it is operating on HSPA+ and the Z3 is operatiing on 4G LTE. Now I don't now why this is happening.

I'm pretty sure that the Xperia V wasn't 4G-capable, so it will ignore any LTE signal seen whereas the Z3 is likely set to prefer 4G/LTE. If there's any usable 4G signal it might be connecting regardless of strength.

Look in Settings/More/Mobile networks/Preferred network type, and set it to WCDMA (preferred)/GSM. Restart the phone and see if the HSPA+ performance is improved.

@Hadron is quite correct about the Z3's frequency support; the only AT&T band lacking in the D6603 is LTE Band 30 (2300MHz). Every other HSPA/LTE band is supported.

 

[jungleexplorer]

Okay. I have had my new Z3 for a while now and I love everything about the phone, accept for the reception quality. I am on AT&T and I travel in the same area routinely and I always had great reception in my normal travel area with my old Xperia V. At my home I always had 4 to 5 bars of signal. My new Z3 never gets more then 1 bar, if any. I almost never had dropped calls on my V no matter where I went. My Z3 drops calls all the time. My mom lives 150 miles away and I go to visit her at least twice a month. Many times I have driven the entire way while talking on my phone (with my BT headset) and never had a dropped call. I have been to her house several times since I got this Z3 and I have no signal about 80% of the time. I could not make a call if my life depended on it. At first I thought that the problem was that my V was using 3G towers and my new Z3 is using 4G towers. But I swtiched my Z3 to 3G only and it still has not signal in areas where my V used to have 4 to 5 bars.

As far as specs go, the Z3 (D6603) has all the same bands that the V has and more. The Z3 works on all the following 3G and 4G bands.

3G Network HSDPA 850 / 900 / 1700 / 1900 / 2100
4G Network LTE band 1(2100), 2(1900), 3(1800), 4(1700/2100), 5(850), 7(2600), 8(900), 13(700), 17(700), 20(800)


These are the bands the Xperia V operates on:

3G bands HSDPA 850 / 900 / 2100

4G bands LTE band 1(2100), 3(1800), 5(850), 7(2600), 20(800)


So what is the problem here? Why is the reception so bad on the Z3?

 

[jungleexplorer]

Hmmm....

 

[zuben el genub]

If you are thinking of buying a non-carrier unlocked phone - go check GSM Arena.
They seem to have the specs for most phones made. All specs, including US and EU bands are listed.

http://www.gsmarena.com/

 

[jungleexplorer]

Humm...???? Sometimes I wonder if people even read the question before answering.

 

[zuben el genub]

Are those the bands listed with your carrier? 1700/2100 are usually TMO.

Some carriers have repurposed bands. TMO is doing that with some old 2 Edge.

I would find your carrier's forum and see what is said about your phone.
Howard forums is snide and has a lot of fanboys, but it will deal with no signal issues and probably has a section for your phone.

I've also read that band up and down can be used differently - I can't explain it but it seems that the same specs in other places besides the US work differently as to how the carrier has modified the bands.

Also, most US carriers are pushing LTE and those might be the bands being switched.
V, TMO and I think ATT are now trying 5G.

 

[jungleexplorer]

I am on AT&T and yes, the Z3 (6603) covers every band that AT&T operates on whether 4G, 3G, or 2G. The band is not the problem. The reception is. I have this same question posted on the AT&T forum and on the XDA forum and have yet to receive an answer. This is what I hate about smartphone forums; unless you have the latest "POPULAR" phone, there is no help. If had a Samusung S5, 6, or 7 or something like that there would be tons of answers here and maybe even something that looks like a solution.

 

[Slug]

This is what I hate about smartphone forums; unless you have the latest "POPULAR" phone, there is no help.

It's not our fault the Z3 isn't "popular" in the US, so don't blame those of us trying to help you.

There's no reason the Z3 shouldn't work fine with your network, so return it as faulty and request a replacement.