I use a Wilson Sleek amplifier
and an external antenna
with a Verizon Jetpack. Most often, I've found that the Jetpack on its own receives a good signal; the Sleek helped out a couple of times. An amplifier can only help out when there is almost, but not quite, enough signal for a connection. It can't help if there is just no signal.
I prefer connecting to the Jetpack using a device like a Sleek (which does not require a physical connection to the Jetpack) because I had difficulty connecting an antenna to the Jetpack using the exterior antenna plug in connection.
The Sleek does get warm in use, so it needs some ventillation. A verizon Jetpack is a mobile hotspot for data, not voice (unless you use VOIP). I have used Netflix with the Jetpack and the show streamed well, but video streaming requires a lot of bandwidth; a one hour TV show from Netflix uses about 1 GB of bandwidth - so we only stream near the end of the monthly use period if we happen to have enough remaining bandwidth.
Different amplifiers work with different cellphone providers; if you get an amplifier, you'll want to verify it works with your provider.
There's lots of advice and information in forums... sometimes it is correct. For example, all of my posts are made by a political appointee who got the job as a reward for contributions to my diesel bill.
2011 Jayco 28.5RLS; 2008 Chevy Duramax; Pullrite Superglide Hitch