1. brusbrother's Avatar
    I recently got the ATT branded unlocked Lumia 640 and am using a sim card from Lycamobile (MVNO using TMobile towers)
    I compared it to a TMobile branded Lumia 521 switching the same sim card between phones and have noticed that there is only ONE reception bar on the ATT L640 phone and TWO bars on the TMo L521.
    This is inside my home where reception is iffy to begin with.
    Any suggestions as to what the issue may be?
    12-12-2015 06:48 PM
  2. libra89's Avatar
    I recently got the ATT branded unlocked Lumia 640 and am using a sim card from Lycamobile (MVNO using TMobile towers)
    I compared it to a TMobile branded Lumia 521 switching the same sim card between phones and have noticed that there is only ONE reception bar on the ATT L640 phone and TWO bars on the TMo L521.
    This is inside my home where reception is iffy to begin with.
    Any suggestions as to what the issue may be?
    My only guess is that one has more bands that T-mobile uses over the other.
    12-12-2015 08:30 PM
  3. Guytronic's Avatar
    T-Mobile service is generally weaker depending on location.
    12-12-2015 09:50 PM
  4. brusbrother's Avatar
    I am stumbling around Google to understand the "bands" and am unsure as to how to compare.
    Found this comparing ATT and TMo 640:
    "They are the same physical hardware, so the radio support will be the same. Both AT&T and T-Mobile (and even Cricket Wireless) carry the RM-1073 model."
    However: ATT 640 Bands 2, 4, 5, 7, 17 and the TMo 640 Bands 2, 4, 5, 7, 17, 28, 12
    OK so that seems to imply that the 640 on TMo and ATT have the same hardware BUT some bands are either locked down or not installed on the ATT
    But my question concerns comparing the TMo 521 to the ATT 640 reception.
    So to now compare the 521 to 640 HERE it would appear that the 640 series has more bands
    The TMo 521 only has Bands 2, 4, and 5 whereas the ATT 640 has 2, 4, 5, and 17
    Does this make sense to anyone?
    12-12-2015 10:02 PM
  5. libra89's Avatar
    Yeah, that's what I think it is. AT&T locked down (or disabled) certain bands. According to T-Mobile docs here, the T-mobile 640 has:
    LTE FDD network12: Band 17 (700MHz), Band 2 (1900 MHz), Band 4 (1700/2100 MHz), Band 5 (850MHz), Band 7 (2600 MHz), Band 28 (700 MHz), Band 12 (700 MHz)
    12-12-2015 11:03 PM
  6. boonesmi's Avatar
    yes AT&T locked down band 12, but your 521 doesn't have that band anyway. most likely its just displaying slightly different on the different models, or maybe the radio is a little weaker on the 640 vs the 521.

    you could always enter field test mode and see exactly what the signal strength is. it usually shows as a negative number, the closer to zero the stronger the signal

    all the other bands that tmobile use are available on an unlocked att lumia 640

    edit to add: to enter field test dial ##3282#
    libra89 and brusbrother like this.
    12-12-2015 11:23 PM
  7. brusbrother's Avatar
    Thanks for the Test Mode info.
    I assumed that I was checking GSM then RSSI. If that is the case, the two phones seem to be about equal, perhaps 1 dBm difference.
    Odd thing: While I was looking at this screen in test mode, the values changed to 0 invalid or N/A. I hadn't made any changes or touched any buttons for that matter. Certain fields like Nicell[0] RSSI disappeared altogether. Immediately swapped the sim between the 640 and 521 when this occurred and had the same results. But now after backing out and reentering Test Mode a few times, they all came back. Don't know what to make of this other than that I should probably stick to my day job!
    Right now the card is installed in the 640 and all values are reporting valid information.
    Is this a momentary failure of the sim/cell provider at that moment?? My daughter keeps teasing me that our MVNO service provider Lycamobile is Like-a-mobile... but not really!
    Phone and cell data are currently functional as before.
    12-13-2015 04:11 AM

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