I saw the OTR antenna here on Amazon and it worked like a charm

It works ok but is there like a stronger antenna for it that can be bought separate?

I purchased an inside and external antennae for each vehicle to simplify moving it around vehicles

A better antenna will boost that (from what I've researched just plan on getting something better - the little magnetic mount doesn't do much - not sure why they bother).

I installed this in a minivan for work and mounted the larger antenna (available separate) on the rear center of my roof and it gave me enough cable to get the booster to right behind my passenger side door which has a pretty convenient access door and space to mount

it would be that the internal antenna is not as sensitive as it could be,

Poor antenna placement may cause interference with radio when turned on, which is user error

Upgraded antennae

I also can place the antenna in a car mount with the phone and it works great if you use bluetooth for music or talking.

the inside antenna is also kinda weak

The larger wilson antennae is also recommended as it makes a big difference.

The larger wilson antennae is also recommended as it makes a big difference.