CC1310: CC1310

To first go one step back: It's not clear why you ask about a bandpass filter? Could you elaborate a bit on the background for your question? Could you also elaborate on the reason you are looking for a LNA and which datarate etc you are planning to use. 

Note that CC1310 has different filters in the RX path, both in the analog and digital domain. The last filter is a channel filter.

www.ti.com/.../swra542

We are using CC1310 to read WMBUS water mater.RF performance of our HW is same with CC1310 LP.But custumers want more.We can read water meters 800meter far from our device.Custemers need 2 km.We are using 868Mhz frequency.So we will do 2 design.One of them is using CC1310 and CC1190 like CC1190 LP.I did desing a custom bord and I will try it on our HW.But Our device is far from antenna in field.Our custemer place device far from antena.Distance is 15m between them.They are using N type omni antenna .RF cable is great which they use for it but we suspected for this application.Because of this we want to use just LNA at antenna side.LNA will be near antenna.thus mybe we can improve RX performance.Also we send power on RF cable for LNA.Can I use B39871B3725U410 filter like your CC1190 LP?

Which WMBUS mode are we looking at here? 

Looking at what would be possible: 

A LNA can improve the sensitivity about 3 dB. If you use https://www.ti.com/tool/RF-RANGE-ESTIMATOR, how much do you need to improve sensitivity to get 2 km range? 

We are using T1 and C1 modes

T1 and C1 is 100 kbps, then I get an estimate showing ~ 250 m with the following setup:

This indicate that when you have tested some of the parameters are different from what I have used here. Which one(s)? 

we are using 5db antenna.Also meter is Line of side in field.