PA28 PLT IS CONFUSED ABOUT LOC AND GS RESPONSES WHILE SHOOTING PRACTICE ILS APCHS. LATER DISCOVERS TOWER HADN'T CHANGED ILS TRANSMITTERS WHEN SWITCHING RWYS.

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A FELLOW PLT AND I WENT UP TO FLY APCHS TODAY FOR CURRENCY. I'M THE PF. WE FLEW THE ILS RWY 35 AT MHT TO A MISSED TWICE. ON THE SECOND MISSED; APCH TELLS US THEY'RE CHANGING RWYS AND THEY'LL SET US UP FOR THE ILS RWY 17 INSTEAD. WE'RE VECTORED AROUND A BIT. WE GET A CLOSE AND RELATIVELY SHARP TURN TO FINAL APCH COURSE AND IT'S THEN THAT I NOTICE THE CDI NEEDLE IS DEFLECTED THE WRONG WAY. I HADN'T REALLY BEEN PAYING ATTN TO IT; FOCUSING ON ASSIGNED HDG AND MY HANDHELD GPS INSTEAD. I WAS CONFUSED; AND KEPT CHASING THE NEEDLE; ONLY TO HAVE IT DO EXACTLY THE OPPOSITE OF WHAT I EXPECTED BASED ON THE CORRECTIONS I WAS MAKING. I CHKED THE CHART 109.1; CHKED NAV 2 109.1. I GOT FIXATED ON THINKING I SOMEHOW PULLED OUT THE WRONG CHART; OR TUNED THE WRONG FREQ. I TURNED ON THE AUTOPLT IN APCH MODE THINKING MAYBE I WAS JUST DISORIENTED. THE AUTOPLT DID A WORSE JOB THAN I WAS DOING. I STARTED TO THINK THE CDI WAS REVERSE SENSING. I SWITCHED THE AUTOPLT TO REVERSE MODE AND IT STARTED FLYING THE CORRECT COURSE; EVEN THOUGH THE CDI WAS REVERSED. THAT CONFIRMED THAT THE CDI WAS REVERSE SENSING. I KEPT LOOKING AT THE CHART THINKING I MISSED SOMETHING. I ASKED MY SAFETY PLT TO VERIFY THE CHART AND THE FREQ. MEANWHILE; I GOT LOW -- A COUPLE HUNDRED FT LOW. I'M SO FIXATED ON THINKING I'VE SCREWED SOMETHING UP -- RADIO NOT SET RIGHT; DIDN'T READ THE CHART; I HAD TO HAVE MISSED SOMETHING -- THAT I'M NOT PAYING ENOUGH ATTN. LUCKILY IT'S VMC AND I'VE GOT A SAFETY PLT. I'M STILL OUTSIDE THE OUTER MARKER; SO I CLB BACK UP TO GS INTERCEPT ALT. THE GS DOESN'T SEEM RIGHT. IT'S NOT WAY OFF; BUT NOT REALLY MOVING AS I'D EXPECT IT. THERE'S NO FLAG; SO I'M RECEIVING A SIGNAL. AFTER GS INTERCEPT (NEEDLE'S BASICALLY CTRED AT THE MARKER) I START DSNDING. AGAIN; THE NEEDLE'S MOVING A BIT; BUT DOESN'T REALLY SEEM TO BE MOVING ACCORDING TO MY DSCNT RATE. A COUPLE OF MI OUT; SAFETY PLT SAYS; 'I SEE 4 RED LIGHTS ON THE PAPI.' THE GS NEEDLE IS MAYBE 1 DOT LOW. I EXECUTED A MISSED APCH; INFORMING MHT TWR OF THE MISSED. AFTER DISCUSSING THE SITUATION WITH SEVERAL PLTS; I'VE COME TO REALIZE THAT MHT TWR NEVER SWITCHED THE LOC FROM RWY 35 TO RWY 17 WHEN THEY CHANGED RWYS. I IDENTED THE LOC FREQ VIA MORSE CODE IDENT WHEN I FLEW THE APCH INTO RWY 35; BUT DIDN'T IDENT THE LOC AGAIN WHEN I COMMENCED THE APCH INTO RWY 17. HAD I IDENTED THE LOC A SECOND TIME; I WOULD HAVE REALIZED I WAS RECEIVING THE LOC SIGNAL FROM THE RWY 35 APCH END; EFFECTIVELY FLYING AN UNPUBLISHED BACK COURSE APCH WITH A FALSE GS.