[Q] Fix for D800 LTE speeds on T-Mobile (in MIA)? topic

My question, for the story below. I think I did something good, did I do something bad?

I bought a brand new D800 on eBay for use on T-Mobile in the MIAMI market. I fished around in the service menu from the stock rom, and did the following:

• Dialer -> 3845#*800#


• LTE Only -> Modem Settings -> LTE Band Selection


• Select Bands 2, 4, 5, and 17 (based on info from wikipedia for D800)


• Back out to main service menu


• LTE Only -> Modem Settings -> LTE-A CA Setting


• Choose CA Enable / SupportedBandCombination All-enable


• Choose Restart Now

Before I did this, my Speedtest.net results were odd and a bit upside down looking. The downloads were in the 5Mb/s area, and uploads more in the 7-9Mb/s. Naturally I thought that was odd but passed it off as the weirdness of having an AT&T phone on T-Mobile.

After my fiddling, the speeds were dramatically different. I was looking at 10-15 (one night, 20) Mb/s down, and 6-10 Mb/s up.

I did this fiddling because I found the service menu when looking to fix a touch firmware issue. I DID NOT do this because I knew what I was doing. I just figured I'd be able to reset if I messed things up bad enough. I'm not even sure which of the above two things did the trick.

So, did I unwittingly do something really dumb/bad?