AT72 CREW RETURNED TO THEIR DEP ARPT BECAUSE OF ERRATIC NDB AND ILS SIGNALS. THIS HAPPENED AT NIGHT; IN IMC; WHEN THE TWR AND TRACON WERE CLOSED.

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WE APCHED AVL FROM THE SW. WE WERE TOLD BY ZTL THAT AVL WAS SET UP FOR THE ILS RWY 34. TWR/APCH AT AVL CLOSED EARLIER. OUR CLRNC FROM ZTL FOR THIS NON RADAR ILS WAS TO MAINTAIN 6000 FT UNTIL BROAD RIVER NDB 379 DEG RADIAL (BRA); CLRED FOR THE ILS RWY 34 AVL. MY NAV RADIOS WERE TUNED AND IDENTED FOR THE ILS 110.5 IAVL; HAVING BRA SELECTED IN MY ADF. I ASKED FO TO KEEP HIS NAV #2 ON SUGARLOAF MOUNTAIN VOR; WITH THE COURSE 233 DEGS OFF OF THE VOR TO HELP IDENT PASSAGE OVER BRA. THIS WAS TO DOUBLECHK OUR POS DUE TO OUR SOMEWHAT DEGRADED RECEPTION OF BRA BY THE ADF. FO ALSO HAD ACCESS TO THE BRA ADF NEEDLE ON HIS SIDE. I HELD DME OFF OF SUG AS WELL ON MY SIDE. ONCE BRA WAS REACHED; I BEGAN PROC TURN OUTBOUND AND DSNDED FIRST TO 5100 FT (TO AVOID A POSSIBLE TERRAIN ALERT). ONCE INBOUND; I DSNDED TO 4400 FT. AT THIS POINT; FO NAV EQUIP WAS ALSO SET UP ON 110.5 IAVL; ILS RWY 34. WE BOTH WERE HOLDING THE DME OFF OF SUG. WITH AUTOPLT ENGAGED; THE APCH WAS THEN ARMED; THE LOC CAPTURED; FOLLOWED BY THE GS. FO SET IN OUR MISSED APCH ALT AND ADF TO 357 DEGS FOR KEANS (IM). ALL WAS NORMAL ON APCH UNTIL APPROX ENNKA; ON LOC AND GS. WE RECEIVED A TERRAIN ALERT. I IMMEDIATELY DISENGAGED THE AUTOPLT AND LEVELED OFF ON THE LOC. THE ALERT WENT OUT ALMOST IMMEDIATELY; AT WHICH TIME I HAD FO EXTEND FLAPS AND GEAR IN AN EFFORT TO CONTINUE THE APCH. MOMENTS LATER; THE GS BEGAN ACTING ERRATICALLY. WE WENT FROM 1 1/2 DOTS HIGH TO SLIGHTLY LOW VERY RAPIDLY. A CORRESPONDING GS ALERT WAS GIVEN BY THE GPWS AT WHICH TIME I IMMEDIATELY INITIATED A GAR. I DO NOT BELIEVE WE EVER DSNDED BELOW 3000 FT MSL ON THIS FIRST ATTEMPTED APCH. UPON ENTERING THE HOLDING PATTERN AND CONTACTING ZTL; ATC ADVISED IT WOULD BE NECESSARY TO CLB HIGHER FOR RADAR COVERAGE. WE COMPLIED; TO 6000 FT OR 7000 FT (I'M NOT CERTAIN WHICH). OUR INTENTIONS TO ATC WERE TO RETURN TO BRA AND TRY AGAIN. ATC GAVE US A 160 DEG HDG TILL RECEIVING BRA; MAINTAIN 6000 FT; CLRED FOR THE ILS RWY 34. DURING THIS TIME; FO REIDENTED IAVL AND BRA ON BOTH SIDES. BRA WAS AGAIN SOMEWHAT DEGRADED IN RECEPTION; BUT APPEARED RELIABLE FOR NAV. AS WE FLEW S TOWARDS BRA; WE ATTEMPTED TO REACH COMPANY ON RADIO AND OPS. FO ALSO INFORMED THE PAX OF OUR INTENTIONS. BOTH NAV RADIOS WERE NOW SET ON 110.5; HOLDING DME OFF OF SUG AND ADF ON BRA (BOTH SIDES). WE DID NOT HAVE A RADIAL TUNED TO EXACT OUR POS OFF OF SUG. AT APPROX 12.8 DME; BRA APPEARED TO SHOW STATION PASSAGE. THE BEARING INDICATOR SWUNG AROUND TO THE R TO SHOW STATION PASSAGE. WE BEGAN A TEARDROP PROC TURN OUTBOUND SLOWLY DSNDING; FIRST TO 5100 FT AND ON TO 4400 FT INBOUND. AS WE INITIATED THE INBOUND TURN; WE NOTICED THE ADF NEEDLE AGAIN SWING TO THE REAR AS IF WE WERE N OF BRA; AND NOT S. THE LOC NEEDLE WAS VERY SENSITIVE; AS IF WE WERE CLOSE TO THE FIELD. HINDSIGHT IS THAT WE WERE. AT THE TIME; WITH OUR EXACT POS IN QUESTION; I INITIATED A SECOND GAR PROC; CLBING TOWARD 6000 FT AND REQUESTING 8000 FT TO OBTAIN RADAR COVERAGE ASAP. WITH RADAR CONTACT ASSURED; I ASKED FO TO DIAL UP SUG ON HIS SIDE TO EXACT OUR POS. THIS POS WAS NOW APPROX N OF KEANS ABOUT 5 MI. REALIZING A RUSHED SECOND ATTEMPT WITHOUT SUG AS A BACK-UP AND A POSSIBLE ADF MALFUNCTION; I ASKED ATC WHAT ALT HE WOULD NEED TO KEEP ME IN RADAR COVERAGE TO BRA. HE INDICATED APPROX 6000 FT. I REQUESTED 6500 FT VECTORS TO BRA; FIGURING I COULD GET DOWN TO 4400 FT IN THE PROC TURN IN ONE MORE ATTEMPT. APCHING BRA; ATC INDICATED WE WERE 3 MI N OF BRA. THE ADF NEEDLE YET AGAIN BEGAN TO SWING 30 DEGS L FOLLOWED BY 30 DEGS R; ALTHOUGH NO INDICATION OF POSSIBLE STATION PASSAGE THIS TIME. BECAUSE ADF IS REQUIRED FOR THE APCH AND THE APCH WAS TO BE CONDUCTED IN A NON RADAR ENVIRONMENT; I FELT THE SAFEST COURSE OF ACTION WAS TO NOT ATTEMPT ANOTHER APCH; BUT RATHER RETURN TO ATL. WE CALLED COMPANY AS SOON AS PRACTICAL AFTER CONSULTING WITH ATC ABOUT OUR DECISION TO RETURN TO ATL. COMPANY MADE THE SUGGESTION TO TEST THE ADF ON THE WAY BACK INTO ATL. USING REDAN 266 FOR RWY 26L BACK INTO ATL; WE OBSERVED NOTHINGOUT OF THE ORDINARY. MY ONLY THOUGHTS ON THE FIRST APCH ARE: IF I WAS IN A DIRTY CONFIGN AND PERHAPS SLOWER; MAYBE I COULD HAVE AVOIDED THE TERRAIN ALERT AND SUBSEQUENT GS ALERT. MY MISTAKE ON THE SECOND APCH WAS TO SOLELY RELY ON BRA ADF AND DME OFF OF SUG TO IDENT MY POS. THIS IS EASY TO DO BY BEING RUSHED ON A SECOND APCH; ALLOWING ONESELF TO BE PREOCCUPIED BY OTHER TASKS. I COULD NOT HAVE PREDICTED BRA NAV DIFFICULTIES; HOWEVER; IF I BACKED THAT UP WITH A RADIAL OFF OF SUG; I WOULD NOT HAVE INITIATED THE PROC TURN FOR THE SECOND APCH. THIS APCH IS DYNAMIC BECAUSE USING SOLELY DME OFF OF SUG TO SUPPLEMENT THE ADF NEEDLE PUTS ONE AT A POINT WHERE IT MIGHT BE EASY TO MISTAKE BRA. EXAMPLE BRA IS 12.8 MI OFF OF SUG AT 233 DEGS. DIRECTLY OVER THE ARPT YOU WILL BE AT 280 DEGS AND APPROX 13 MI. I BELIEVE THE DISTANCE FROM SUG TO ENNKA TO APPROX 9 OR 10 MI. BASICALLY; RETURNING FROM KEANS; THE DME WILL COUNT DOWN TO AND THROUGH 12.8 TO SOME LOWER DISTANCE; THEN INCREASE BACK TO 12.8 AT BRA. HOWEVER; WHAT OCCURRED ON OUR FLT WAS AN APPARENT STATION PASSAGE ACCORDING TO ADF THAT WAS IN ERROR; WHICH COINCIDENTALLY OCCURRED AT THE FIRST 12.8 DME AREA JUST S OF THE ARPT. I BELIEVE NOW THAT OUR PROC TURN WAS INITIATED ON THIS SECOND APCH IN ERROR NEARLY 8 MI N OF BRA. AS FOR THE THIRD ATTEMPT THAT NEVER HAPPENED. PERHAPS; I SHOULD HAVE ALLOWED ATC TO CALL BRA FOR ME. BUT CONSIDERATION OF THE WAY THE ADF WAS BEHAVING AND THE 2 PREVIOUS MISSED APCHS LED ME TO BELIEVE THE SAFEST COURSE OF ACTION WAS TO PROCEED BACK TO ATL AND PLAY ARMCHAIR QUARTERBACK LATER. FROM ATC'S STANDPOINT; MY ONLY QUESTION IS; WHY DID THEY NOT ASK ABOUT MY POS ON THE SECOND APCH? I MUST HAVE DISAPPEARED FROM THE RADAR SCREEN EARLIER THAN THEY ARE USED TO SEEING. PERHAPS THEY MISSED IT; BUT PERHAPS ONCE AN ACFT GOES MISSED AT AN ARPT LIKE AVL; MAYBE MORE ATTN NEEDS TO BE PAID TO THAT ACFT. AFTER LNDG; I TALKED WITH MAINT; OUR COMPANY DISPATCHER AND MOST SIGNIFICANTLY WITH ZTL. I SPOKE IN GREAT DETAIL; OUTLINING WHAT I HAVE SAID HERE. I WAS HOPING TO FIGURE OUT WHETHER OUR ACFT'S ADF RECEIVER WAS HAVING THE DIFFICULTY; OR IF BRA NDB MIGHT BE CAUSING A PROB. ALSO; TO SEE IF THERE WAS ANY PROB WITH THE GS ON RWY 34. I ADMITTED MY POSSIBLE ERROR IN RELYING SOLELY ON BRA AND SUG DME FOR IDENTING BRA STATION PASSAGE (SECOND APCH). I HAVE BEEN TO AVL COUNTLESS TIMES OVER THE PAST 3 YRS AS A CAPT ON THE ATR AND SEVERAL TIMES AS A FO ON THE BRASILIA. WHILE I HAVE EXPERIENCED SEVERAL NUISANCE TERRAIN ALERTS; I HAVE NOT EXPERIENCED THE NDB/ADF AND GS PROBS THAT I ENCOUNTERED LAST NIGHT.