Hello, I'm trying to fing a gsm module that works on T-Mobile so I can send text messages. I founds a lot of gsm modules But I don't know which one will work. I'm looking at what frequencies does T-Mobile uses and it is all over the place. Plus the whole 4G lte and the 5G. I'm nore sure what to really use for a module. I'm in the USA and I need help to figure out which module I can use on a arduino. Can you help me out please?
Joseph
The cellular frequency has nothing to do with sending a SMS Text message. Next, you want to give this a read. You will need the called out shield or similar.
If you want to play around with just sending a SMS Text from your home PC there is a simple script (.vbs) you can run. Possibly with your Arduino on a serial port.
Cellular carriers use a text message gateway you may need. For T-Mobile it should be number@tmomail.net. The following assumes a Windows operating system. If you want to try an experiment copy the following code and paste it into notepad.
CreateMailMessage "number@tmomail.net", _
"test message from VBScript", _
"test message from VBScript"
Sub CreateMailMessage(strTo, strSubject, strBody)
Set appOutlook = CreateObject("Outlook.Application")
Set msg = appOutlook.CreateItem(olMailItem)
With msg
.To = strTo
.Subject = strSubject
.Body = strBody
.Send
End With
End Sub
Save the file to for example your desktop on your PC and save it as a .vbs file type. File > Save As > File Name (pick a name followed by .vbs) File Type .vbs. Saved on your desktop just double click the saved file and check your phone for a text. Modify the code for whatever text you want to send. I never tried calling the code up using an Arduino. There should be a way tpo go about it.
Ron
Look for an SMS module that supports at least 4G LTE.
Example: SIM7600 4G GSM with Arduino | AT Commands, Call, SMS
Before you buy, it would be a good idea to find out if the module actually does work with T-Mobile.
If your device will be in wifi range and the SMS target phone service provider allows SMSs via email (the text message gateway that @Ron_Blain mentioned), then you don't need a GSM module: all you need is an ESP8266, ESP32, or other Arduino with wifi.
For example, I can email myself an SMS by sending an email to something like myCellNumber@sms.cricketwireless.net
Each carrier has a different @xxxxxx.yyy
You can easily test this by using your favorite email program (Outlook, Gmail, etc.) to send an email "text" to yourTargetTextNumber@xxxxxx.yyy
For sending emails (and texts via email), the Mobizt ESP-Mail-Client library works well for me.
Good point, I should have mentioned that. Thought about it and promptly forgot about it. 
Much easier way to go.
Ron
Hello all, Thank you for the reply back. My problem is not coding. My problem is I do not know which shield or module would work on the Tmobile network. I boughta few that was cheap thinking they would work. Because they stated it will work on the Tmobile network and that was a lie. I do not know which one will work on the USA T-mobile network.
Joseph
Just about any of them should work with the proper coding. This may go much better with a link to any modules you have and include the code you are using. T-Mobile in the US should use the number@tmomail.net so you use yout ten digit number with @tmomail.net which is the T-Mobile gateway. Just about any shield should work. Did you read through the link I provided earlier?
Ron
the modules I have are https://www.ebay.com/itm/223564440148 and https://www.ebay.com/itm/322664879324. The second one I just got in this 3 days ago but I haven't tried it yet. the first one doesn't work and I can not get it to see a signal from a tower.
Joseph
Well let's hope the second one works. Pretty big price difference between them. No clue why the first module hasn't worked?
Ron
Well the first one won't work on T-Mobile USA because as it says on the PCB legend it's 900-1800 dual band which are European GSM bands! Tmo would be 800-1700.
When I investigated T-mobile, they lease space on the AT&T system.
That may be true as they may well have switched off their GSM already. But the USA does not use the 900/1800 spectrum anywhere AFAIK. The equivalent is 800/1900 (sorry not 1700). So a 900/1800 device will not see any base station transmissions in the USA. When we used to only have quad band GSM handsets for international roaming, they did 900/1800 in EU and 800/1900 in USA. For my sins I spent some unhappy times selling small GSM base stations to TMO both in UK and USA.
Hello all Thank you for the reply back. As I'm searching for a gsm module or shield. To use on the Tmobile network. I'm finding it hard to find one. I have no clue what Gsm module will work.
Joseph
Did you try Google? One of the first hits on arduino gsm:
Quad-band 850/900/1800/1900MHz - connect onto any global GSM network with any 2G SIM (in the USA, T-Mobile is suggested)
...for as long as T-Mobile keeps it alive...
PS: did you read the posts that said you don't even need a GSM module or shield to send SMSs, under certain circumstances?
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