THE ACFT STRUCK A NON-DIRECTIONAL RADIO BEACON TOWER WHILE ON AN ILS DME RWY 05 INSTRUMENT APPROACH TO THE KUPARAK OIL FIELD AIRPORT. INVESTIGATION REVEALED THAT WX ISSUED TO THE ACFT INCLUDED AN INDEFINATE 200 FT SKY OBSCURED CONDITION & VISIBILITY OF 1 1/4 MILES. BOTH THE CAPTAIN & CO-PLT STATED THAT THEY COULD SEE THE OTHER END OF THE RWY. THE DECISION HEIGHT FOR THE APPROACH IS 316 FT MSL; THE ANTENNA HEIGHT WAS 35 FT, AT THIS POINT THE ACFT SHOULD BE 250 FT ABOVE THE GROUND AND OVER THE NON-DIRECTIONAL BEACON TOWER. INVESTIGATION DID REVEAL THAT THE TOWER USED TO BE LOCATED 2800 FT OFF THE APPROACH END OF RWY 05, BUT WAS MOVED TO 1775 FT FROM THE APPROACH END OF RWY 05. EXISTING APPROACH PLATES DID NOT DISPLAY THE NEW LOCATION OF THE ANTENNA OR THE FACT THAT THE ANTENNA WAS ONE FT HIGHER THAN THE MAXIMUM AUTHORIZED BY THE FCC. Probable Cause: