Long antenna cable possible?

[MrGlasspoole]

I have the problem that i need the main microcontroller in the basement in the central heading room.
But i want the antenna in the middle of the ground floor to have signal around the house.

One way solving that would be using a small microcontroller with the RFM69 connected to the one in the basement via RS485.
But that makes coding complicated and i have to do code changes every time on two devices.

Is 6-8 meters antenna cable possible? Are there antenna amplifiers like for radio/TV?

[captcha]

Anything is possible..

If you had a decently matched antenna (<1.5:1 SWR) and fed it with decent cable you could lose up to 30% of your power with 6m of RG-8X @ 868MHz. LMR-400 will hold up better with about 17% loss. Just for fun, RG-58 will cut your power in half and RG-174 takes a whopping 75% away.
http://kv5r.com/ham-radio/coax-loss-calculator/

SWR higher than that and you might as well use a flashlight for your signaling protocol..

My suggestion would be to extend your sensors from the basement to the ground floor.