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The booster does produce heat as does your phone, especially in hotspot mode and even more so if you are charging it at the same time. What helps is to put something under the phone to give it a little air pocket, maybe a pen under one side.
Using the boosters USB charging port adds another heat source so if I have to charge a device, I use a exterior charger.
Boosting in a area with good signals probably isn't going to be all that impressive. That said there are other ways besides bars to see what is happening to the signal strength. The easiest for me is to load a free app called network cell info lite. It will show you the dBa of your signal as well as has a map that shows you what cell tower you are connected to. That map shows you what direction to point the antenna, the dBa meter lets you fine tune it. The lower the dBa, the better the signal.
Knowing what direction to point the antenna is important because you can weaken your connection if you are off, cause the phone to disconnect or even connect to a antenna much farther off. Directional antennas are wonderful as long as they are pointed at the tower. Omni directional antennas are easier but produce weaker results.
Another thing about being in a metro area is there may be multiple towers and multiple bands on those towers for your device to be connected to. I have been frustrated trying to aim the antenna for my Cricket phone on AT&T because it uses LTE for data and 4G for talk and text. In Prescott they were not on the same tower so I had to either aim at one or the other depending on what service I was using or split the difference and accept what I got on both. In Cottonwood there were multiple towers and the connection was bouncing all over the place.
Another thing is bands. I have connected to a tower and watched my signal go up, then down and then up again. When you look at a tower and see multiple levels of antennas, each is for a different company. On each level you will see different shapes of antennas, each of those is for a different band. Your device can bounce around on those bands looking for one that isn't congested seeing a different signal strength from each.
A example of mispointing the antenna is like here on Gooseberry mesa where Verizon and AT&T light it up when I connect to a tower south west of me. My Sprint however shows one bar of service unless I drop it into the cradle, then it shows no service at all. I have to have the antenna pointed east and then the Sprint devices get a good signal and work just fine.
Another way to see where towers are is to go to cellreception.com. It will show you all the towers in your area and you can tell it to show you those towers that your company owns. That second part can be misleading because your company doesn't have to own the tower, in fact they likely rent space on more towers than they own.
I hope it helps. As with any tech you have to learn the ins and outs to get the most out of it.
