1.The antenna on the Belkin does not unscrew but is soldered to the internal cct.bd.
2.It operates at 2.4GHz not 5.6GHz so the "parabolic" would probably be inefficient.
3.If you don't have Line of Sight between the 2 locations it probably won't work.
Attenuation caused by 18in concrete wall is 18dB
Attenuation caused by 27in external concrete wall is 53dB