GPS 18 Technical Specifications (190-00307-00) Rev. DPage 204.2.14 DGPS Beacon Information (PGRMB)NOTE: The GPS 18 products do not support PGRMB at this time.$PGRMB,<1>,<2>,<3>,<4>,<5>,K,<6>,<7>,<8>*hh<1> Beacon tune frequency, 0.0, 283.5 to 325.0 kHz in 0.5 kHz steps<2> Beacon bit rate, 0, 25, 50, 100, or 200 bps<3> Beacon SNR, 0 to 31<4> Beacon data quality, 0 to 100<5> Distance to beacon reference station in kilometers<6> Beacon receiver communication status (0 = Check Wiring, 1 = No Signal, 2 = Tuning, 3 =Receiving, 4= Scanning)<7> DGPS fix source (R = RTCM, W = WAAS, N = Non-DGPS Fix)<8> DGPS mode, A = Automatic, W = WAAS Only, R = RTCM Only, N = None (DGPS disabled)4.3 BAUD RATE SELECTIONBaud rate selection can be performed by sending the appropriate configuration sentence to the GPS sensoras described in the $PGRMC Section 4.1.2 Sensor Initialization Information (PGRMI), field <10>.4.4 MEASUREMENT PULSE OUTPUT (GPS 18 LVC & 18-5Hz ONLY)4.4.1 One-Pulse-Per-Second (PPS) Output (GPS 18 LVC Only)The highly accurate one-pulse-per-second (PPS) output is provided for applications requiring precisetiming measurements. After the initial position fix has been calculated, the PPS signal is generated andcontinues until power down. The rising edge of the signal is aligned to the start of each GPS second within1 μs for all conditions in which the receiver has reported a valid and accurate position for at least theprevious 4 seconds.The NMEA 0183 sentences that follow each rising edge of the PPS signal tell when you were and whereyou were at that previous rising edge of the PPS signal, beginning with the GPRMC sentence as the leadsentence in any particular NMEA 0183 record.Regardless of the selected baud rate, the information transmitted by the GPS 18 series products isreferenced to the pulse immediately preceding the NMEA 0183 RMC sentence.The accuracy of the one-pulse-per-second output is maintained only while the GPS receiver is computing avalid position fix. To obtain the most accurate results, the one-pulse-per-second output should be calibratedagainst a local time reference to compensate for cable and internal receiver delays and the local time bias.The default pulse width is 100 ms, however; it may be programmed in 20 ms increments between 20 msand 980 ms as described in $PGRMC Section 4.1.2 Sensor Initialization Information (PGRMI), field <13>.4.4.2 Five-Pulse-Per-Second Output (GPS 18-5Hz Only)The highly accurate five-pulse-per-second output is provided for applications requiring precise timingmeasurements. After the initial position fix has been calculated, the GPS 18-5Hz generates the pulse signal,which continues until power down. The rising edge of the signal is aligned to the start of each GPS secondwithin 1 μs for all conditions in which the receiver has reported a valid and accurate position for at least theprevious 4 seconds.The NMEA 0183 sentences that follow each rising edge of the Measurement Pulse Output signal tell whenand where you were at that previous rising edge of the Measurement Pulse Output signal, beginning withthe GPRMC sentence as the lead sentence in any particular NMEA 0183 record.Regardless of the selected baud rate, the information transmitted by the GPS 18-5Hz is referenced to thepreceding five times per-second output pulse.The accuracy of the five-pulse-per-second output is maintained only while the GPS 18-5Hz can compute avalid position fix. To obtain the most accurate results, the five-pulse-per-second output should be calibratedagainst a local time reference to compensate for cable and internal receiver delays and the local time bias.
