I believe I have read several places that multiple antennas need some separation. So, placing one on each side of the cab, like you see big truckers do, doesn't work well. Our trucks are too narrow. If you want dual antennas, opposite corners of the truck might be better.
In my opinion, just stick with one good quality antenna with optimal placement. Longer ones are often better.
Here is a thread that discusses some of this. I kind of picked the middle of the duscussion. So, scroll backward and forward a bit to get all the info.
Post in thread 'What did you do to your Ranger today? (Part Deux!)'
https://www.therangerstation.com/fo...ur-ranger-today-part-deux.186616/post-2046027