Narrative:

On several occasions, I have had difficulty getting a response from the phoenix, az, approach control when 25-30 NM out from the center of the phx TCA. I believe this to be caused by two conditions. The controller's antennas may be blocked by ground interference. Since I have been able to raise a controller on a different frequency after having lost the one on my last assigned frequency, it would appear that the second frequency's antenna may be better placed for reception out at the perimeter of TCA. Oddly, the low altitude frequency works better for me when at the higher altitude where I lose the higher altitude controller. At the 25-30 mi position, my aircraft tail or fuselage may shadow the xmissions which are coming from the aircraft's antennas. The latter on my plane are 90 degree bent wires which are mounted just forward of the tail and are low profile in order to lie under the fiberglass dorsal fin. On a VFR flight from a small airport near tucson to prescott, az, in the vicinity of casa grande, az, I tuned in the DME radio to salt river VOR near sky harbor airport (phx international). It read 27 NM south. I called phx approach and by the time they responded I was at or just inside the phx TCA. The controller commented on my 'entering the TCA west/O a clearance.' the sunday afternoon traffic was light and he immediately gave me a clearance with the suggestion to call next time from further out, which I shall do...it was a bit close. I continued under several controllers across the TCA northward to about 22 mi past the TCA center and received a transmission that was breaking up saying I was unreadable. I turned the plane 90 degree right to reduce the shadowing effect of the aircraft tail and tried the transmission again. There was no improvement so I switched to the frequency normally used for flts below 5500'. (I was still at 8500'). It was clear, which led me to believe that the first antenna was blocked by terrain interference (there are many mountains around phoenix). Since I have had this experience on other occasions when approaching to land at sky harbor, and this causes unnecessary repeat or relayed xmissions, I believe safety would be served if the antennas serving some of the phx frequencys were checked and possibly moved to mountain top locations.

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Original NASA ASRS Text

Title: SMA HAS TROUBLE CONTACTING TRACON AND ENTERS TCA PRIOR TO CONTACT.

Narrative: ON SEVERAL OCCASIONS, I HAVE HAD DIFFICULTY GETTING A RESPONSE FROM THE PHOENIX, AZ, APCH CTL WHEN 25-30 NM OUT FROM THE CTR OF THE PHX TCA. I BELIEVE THIS TO BE CAUSED BY TWO CONDITIONS. THE CTLR'S ANTENNAS MAY BE BLOCKED BY GND INTERFERENCE. SINCE I HAVE BEEN ABLE TO RAISE A CTLR ON A DIFFERENT FREQ AFTER HAVING LOST THE ONE ON MY LAST ASSIGNED FREQ, IT WOULD APPEAR THAT THE SEC FREQ'S ANTENNA MAY BE BETTER PLACED FOR RECEPTION OUT AT THE PERIMETER OF TCA. ODDLY, THE LOW ALT FREQ WORKS BETTER FOR ME WHEN AT THE HIGHER ALT WHERE I LOSE THE HIGHER ALT CTLR. AT THE 25-30 MI POS, MY ACFT TAIL OR FUSELAGE MAY SHADOW THE XMISSIONS WHICH ARE COMING FROM THE ACFT'S ANTENNAS. THE LATTER ON MY PLANE ARE 90 DEG BENT WIRES WHICH ARE MOUNTED JUST FORWARD OF THE TAIL AND ARE LOW PROFILE IN ORDER TO LIE UNDER THE FIBERGLASS DORSAL FIN. ON A VFR FLT FROM A SMALL ARPT NEAR TUCSON TO PRESCOTT, AZ, IN THE VICINITY OF CASA GRANDE, AZ, I TUNED IN THE DME RADIO TO SALT RIVER VOR NEAR SKY HARBOR ARPT (PHX INTL). IT READ 27 NM S. I CALLED PHX APCH AND BY THE TIME THEY RESPONDED I WAS AT OR JUST INSIDE THE PHX TCA. THE CTLR COMMENTED ON MY 'ENTERING THE TCA W/O A CLRNC.' THE SUNDAY AFTERNOON TFC WAS LIGHT AND HE IMMEDIATELY GAVE ME A CLRNC WITH THE SUGGESTION TO CALL NEXT TIME FROM FURTHER OUT, WHICH I SHALL DO...IT WAS A BIT CLOSE. I CONTINUED UNDER SEVERAL CTLRS ACROSS THE TCA NORTHWARD TO ABOUT 22 MI PAST THE TCA CTR AND RECEIVED A XMISSION THAT WAS BREAKING UP SAYING I WAS UNREADABLE. I TURNED THE PLANE 90 DEG R TO REDUCE THE SHADOWING EFFECT OF THE ACFT TAIL AND TRIED THE XMISSION AGAIN. THERE WAS NO IMPROVEMENT SO I SWITCHED TO THE FREQ NORMALLY USED FOR FLTS BELOW 5500'. (I WAS STILL AT 8500'). IT WAS CLR, WHICH LED ME TO BELIEVE THAT THE FIRST ANTENNA WAS BLOCKED BY TERRAIN INTERFERENCE (THERE ARE MANY MOUNTAINS AROUND PHOENIX). SINCE I HAVE HAD THIS EXPERIENCE ON OTHER OCCASIONS WHEN APCHING TO LAND AT SKY HARBOR, AND THIS CAUSES UNNECESSARY REPEAT OR RELAYED XMISSIONS, I BELIEVE SAFETY WOULD BE SERVED IF THE ANTENNAS SERVING SOME OF THE PHX FREQS WERE CHKED AND POSSIBLY MOVED TO MOUNTAIN TOP LOCATIONS.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.