At my home (zip code 98922), my phone will occasionally connect to the Extended LTE network, but will invariable switch back to the 1x Network.
Here is an example, I reboot my phone and it's connected to LTE.

A few minutes later it's switched back to 1x:

I see that the 1x signal strength is better, is that the only measure used to decide to switch? I'd prefer the higher speed - 1x is useless. Anyone know of a magic incantation to force the phone to stay locked to the LTE network?