Antenna Shananigans

[UkrainianDennis]

I'm having quite the internet situation. My PC is just a few feet away from having a WiFi signal. I just don't know if its a good idea to buy a rp-sma cable to extend the antennas, or just to buy a repeater or power line adapter. Im looking for something that will get me the best internet speed. I don't know if the cable will have huge internet degradation or if its a good idea. I'm currently planning to buy a 30ft long rp-sma cable to extend the antenna directly above my router. 

Notes:

~router is on first story

~pc is on second story

~distance to area directly above router is roughly 15ft, but im going to put cable against wall so it would take roughly 26-30ft.

~in the area directly above the router, i get 60-70mbps on my phone.

 

This is the first time im doing anything with networking, so anything helps. Thank You.

 

amazing ms-paint drawing below.