John,
If you are looking to boost cell service onboard, I can't help. But if you are needing to boost the service at you home, here is a solution that I implemented.
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I found a solution for poor cellphone service. Its a cellphone signal booster that amplifies the mobile signal to and from the nearest cell tower.
We live about 2 miles from the cell tower that provides our signal. This means that we have one bar (on a good day) and we experience dropped calls, missed calls, and failure to originate calls. Our signal level inside the house was about -122 dBm.
So I installed a booster device that uses an outside antenna at the peak of our garage and an inside amplifier and antenna. The outside antenna needed to be aimed correctly and the inside antenna had placement restrictions in relation to the outside antenna.
Bottom line: our mobile signal increased by about 20 dBm and we now have 2-3 bars inside our house. Now out inside signal level is about -100 dBm. So far, no dropped calls or any other bad cellphone behavior.
I bought the amplifier system and the roof mount on Amazon. Less than $150.