The GP was referring to a problem with GPS, not their cellular connection. In any case, I haven't noticed any issues with T-mobile in San Francisco, so maybe T-mobile has some weaknesses unique to the Chicago area.

I'm fully aware but in the context of GPS reception on cellular devices--prompting me to ask what I thought was a tangential question. Apologies that this was such a severe faux pas to end up downvoted into the negatives.

Last time in Chi-town (2016) I had the best signal of the bunch with my TMO (others mostly on ATT/VZ).

Of course, over-subscription is a thing, so maybe things degraded?

Verizon, unfortunately. Though a lot of the issue isn't signal but bandwidth. There are just too many people. You'll have five bars and nothing will load. That's what caused me to leave T-Mobile.

In Chicago, ATT is one of the better ones. It works reliably in the loop as well. Just read the fine print carefully for those extra charges.