Well, you can see the wiring where it goes into the back of the faceplate and into the aerial. Is there any sign of a foil overall screen as well as a braid inside the connections? You may need to look carefully where the outer cable sheath has been cut.
If the wiring is in the wall then it will most likely have been installed when the house was built, in which case it is likely to be the cheapest crappest cable the builders could find (and may or may not be the correct impedance if the builders were cowboys). Do you know if the cable is from when the house was built, or was it put in the walls later?
Can't you ask your neighbour who installed their aerial?
You haven't answered if you have an aerial distribution system. That will not be in the walls, it needs boxes and connections and maybe power to do that. This might be in the loft. Are there any TV wall outlets anywhere else in the house? If there are it's odds on you have a distribution system.