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GPS RECEIVER INTERFERENCE
FROM ACTIVE TELEVISION ANTENNAS
ALCOAST 298/03
P 231400Z JUN 03 ZUI
ASN-A00174000057
FM COMDT COGARD WASHINGTON DC//G-O//
TO ALCOAST
BT
UNCLAS //N16570//
ALCOAST 298/03
COMDTNOTE 16570
SUBJ: GPS RECEIVER INTERFERENCE FROM ACTIVE TELEVISION ANTENNAS
A. USCG G-MOA SAFETY
ALERT, DATED 15 NOV 2002.
B. C2CEN SMEF
ADVISORY NAVSENS-02-002, DTG 241602Z DEC 02.
1. THIS ALCOAST AFFECTS ALL UNITS WHERE GPS RECEIVERS AND MARINE TELEVISION ANTENNAS ARE INSTALLED.
2. THE PURPOSE OF THIS ADVISORY IS TO NOTIFY FIELD UNITS OF A POSSIBLE INTERFERENCE PROBLEM WITH MARINE GPS RECEIVERS ARISING FROM THE OPERATION OF VARIOUS MODELS OF ACTIVE (POWERED) VHF/UHF MARINE TELEVISION ANTENNAS. THIS PROBLEM IS DESCRIBED IN A SAFETY ALERT (REF A) RELEASED BY THE CG OFFICE OF INVESTIGATIONS AND ANALYSIS (G-MOA).
3. THE COMPLETE TEXT OF THE ALERT IS POSTED ON COMDT G-M WEBSITE AT: HTTP://WWW.USCG.MIL/HQ/G-M/MOA/DOCS/11-02.HTM
4. THE TEXT OF THE SAFETY ALERT IS AS FOLLOWS:
SAFETY ALERT-TELEVISION ANTENNAE INTERFERENCE WITH GPS
NOVEMBER 15, 2002 WASHINGTON, DC.
IT HAS COME TO THE ATTENTION OF THE U.S. COAST GUARD AND FEDERAL COMMUNICATIONS COMMISSION (FCC) THAT CERTAIN CONSUMER ELECTRONICS-GRADE ACTIVE VHF/UHF MARINE TELEVISION ANTENNAS ARE CAUSING OPERATIONAL DEGRADATION IN THE PERFORMANCE OF GLOBAL POSITIONING SYSTEM (GPS) RECEIVERS.
THIS INTERFERENCE MAY BE REALIZED AS A DISPLAY OF INACCURATE POSITION INFORMATION OR A COMPLETE LOSS OF GPS RECEIVER ACQUISITION AND TRACKING ABILITY. THE INTERFERENCE IS NOT LIMITED TO THE GPS EQUIPMENT ONBOARD THE VESSEL WITH THE INSTALLED ACTIVE MARINE TELEVISION ANTENNAE. THERE HAVE BEEN REPORTS OF INTERFERENCE OCCURRING ON OTHER VESSELS AND INSTALLATIONS OPERATING UP TO 2000 FEET AWAY FROM VESSELS USING SUCH ANTENNAS.
IN ONE PARTICULAR CASE, THE INTERFERENCE CAUSED THE POSITION OF THE VESSEL AS DISPLAYED ON THE ELECTRONIC CHART TO MOVE ERRATICALLY AND DRAMATICALLY OFTEN ACROSS LARGE EXPANSES OF LAND. AS CAN BE EXPECTED, VARIOUS DATA DISPLAYS INDICATED ERRONEOUS INFORMATION SUCH AS EXCESSIVE SPEEDS. IN THESE INSTANCES THE PROBLEM WOULD OCCASIONALLY CORRECT ITSELF WHILE AT OTHER TIMES REQUIRED RESETTING THE SYSTEM. TO THE VESSELS CREW THESE ANNOYANCES WERE FRUSTRATING AND CAUSED CONCERNS THAT PERHAPS LESS OBVIOUS INACCURACIES WERE OCCURRING. ULTIMATELY THIS AFFECTED THEIR CONFIDENCE IN THE PERFORMANCE OF THE GPS AND ELECTRONIC CHART DISPLAY AND INFORMATION SYSTEM.
IF YOU ARE EXPERIENCING RECURRING OUTAGES OR DEGRADATION OF YOUR GPS RECEIVER OPERATION YOU SHOULD PERFORM AN ON-OFF TEST OF YOUR TV ANTENNA. IF TURNING OFF THE POWER TO THE ANTENNA RESULTS IN IMPROVEMENT IN THE GPS RECEIVER PERFORMANCE, THE ANTENNA MAY BE THE SOURCE OF INTERFERENCE IN THE GPS BAND. IN THAT CASE, YOU SHOULD CONTACT THE MANUFACTURER OF THE ANTENNA AND IDENTIFY THE SYMPTOMS. IF THE TEST IS NOT POSITIVE AND THE GPS INTERFERENCE PERSISTS, CONTACT THE WATCHSTANDER AT THE COAST GUARD NAVIGATION INFORMATION SERVICE AT NISWS(AT)NAVCEN.USCG.MIL / 703.313.5900.
5. ANTENNA MODELS IDENTIFIED DURING INVESTIGATIONS OF GPS INTERFERENCE:
A. TDP (TANDY DISTRIBUTION PRODUCTS) ELECTRONICS - MINI STATE ELECTRONIC AMPLIFIED UHF/VHF TV ANTENNA - MODELS 5MS740, 5MS750, 5MS921.
B. RADIO SHACK CORPORATION - LONG RANGE AMPLIFIED OMNI DIRECTIONAL TV ANTENNA - MODEL 15-1624, MANUFACTURED BETWEEN JAN 2000 - APR 2002, HTTP://SUPPORT.RADIOSHACK.COM/SUPPORT_VIDEO/DOC68/68779.HTM
C. SHAKESPEARE CORP - SEAWATCH 2040/CODE DATE 02A00, 2050/CODE DATE 03A00 (CODE DATES ARE FOUND ON THE ANTENNA POWER SUPPLY), WWW.SHAKESPEARE-MARINE.COM/ANTENNAS/TV/SAFETYALERT-TVANTENNAS.HTM
6. QUESTIONS CONCERNING THIS ALCOAST SHOULD BE DIRECTED TO THE NAVIGATION CENTERS NIS WATCHSTANDER 703.313.5900, E-MAIL: NISWS(AT)NAVCEN.USCG.MIL OR AT WWW.NAVCEN.USCG.GOV
7. INTERNET RELEASE AUTHORIZED.
8. RELEASED BY RADM DAVID S. BELZ, ASSISTANT COMMANDANT FOR OPERATIONS.
BT
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