Garmin SOUNDER 125 Owner's Manual & Reference

Contents

DGPS InterfaceThe last two format settings allow the differential-ready GPS 125 Sounder to accept RTCM DGPS correc-tions in RTCM 104 version 2.0 format. Using DGPScorrections will improve receiver accuracy to 5-10meters, regardless of errors induced by the government’sSelective Availability (SA) program. The RTCM/NONEformat will allow connection to any manually tunedbeacon receiver by using the proper output interface.The baud rate is selectable from the GPS 125 Sounder.The RTCM/NMEA selection controls the GARMINGBR-21 differential beacon receiver. Once a RTCM set-ting has been selected, the GPS 125 Sounder will eitherautomatically try to tune the last frequency and bit rateyou selected or will switch to the default frequency of304.0 kHz with a bit rate of 100 bps if no previous bea-con has been tuned. You may also enter your own fre-quency and bit rate if desired.To enter a DGPS beacon frequency:1. Highlight the ‘FREQ’ field and press F.2. Enter the desired frequency and press F.3. Highlight the ‘RATE’ field and press F.4. Use U and D to select the desired transmit rate.5. Press the F key to confirm your entry.When the GPS 125 Sounder is receiving DGPS cor-rections from the GBR-21, the ‘BEACON RECVR’ sec-tion of the I/O setup page will display the beacon fre-quency and signal strength, as well as the distance fromthe transmitter to the beacon receiver. At the bottom ofthe beacon receiver field, a status message will keep youinformed of DGPS activity:• A ‘Tuning’ message will be displayed while a bea-con signal is being tuned.• Once the beacon signal has been tuned, a‘Receiving’ message will be displayed.• If a beacon signal is tuned and no corrections arebeing received, a ‘No Data’ message will be dis-played.• If a beacon signal cannot be tuned, a ‘No Status’message will be displayed.DGPS InterfaceREFERENCE50The selectable baud rate isavailable for all RTCMinterface options.Once a RTCM option isselected, you must manual-ly tune the beacon receiverfrom the frequency field.