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Lowrance GM 100 goes to Norway

The first project, a power supply box to allow the use of the Lowe Patch Antenna was completed and tested before departure. For operation on the SAS  Boeing 767, the GPS plus Lowe antenna were operated from a 12 volt Camcorder battery. The Lowe antenna was taped to the bottom of the aircraft window using black electrical tape which leaves no residue. I thought there would be a problem getting through security with all that wiring, battery etc. I had to open the bag and explain the contents. Once on the plane, Captain’s permission was obtained for operation once the proper altitude was reached. The flight attendant questioned the system and was told that the Captain had given permission. She did not know what a GPS was!

Operational lock on satellites visible was quickly obtained after approximate location was entered.  Flight was tracked out over Labrador and then operation was suspended for food, sleep etc.until morning when we approached the Norwegian coast near Bergen and flight was tracked to the Oslo area.

 The GM 100 had been loaded with the  maps of the west coastal region of Norway in preparation for a two week vacation to the fjord area.  The mapping detail left a bit to desired in that the closest zoom level was restricted to 3 Nautical miles screen width.  The map for the City of Bergen was inaccurate well beyond the realm of Selective Availability.  I found myself rather high on a hill looking for the harbor area when the GPS indicated my position at the edge of the harbor! 

Once on board the coastal service ship (460 passengers, 50 cars and freight space) the Lowe antenna was taped to the cabin window and the recently purchased 12 v power supply from Radio Shack was powered up using the adapter plug.

The supply is rated for 85 to 240 volts, 50/60 HZ operation. Very satisfactory !! Used it to charge the Camcorder battery when needed. The Lowe antenna remained in the cabin window for the entire trip running whenever the GPS was available, night and day. It was not possible the preplan a route even though the various major stops had been entered in the waypoint list because there were quite a few short duration stops and the ships route was in and out of islands, fjords etc. In a few places, the track went over land and in one area at Lat. 68 the mapping showed roads winding around in the ocean, totally off shore.

While lock was occasionally lost due to lack of sufficient satellites or satellite geometry, operation was quite successful considering the limited view available. 

On deck was another story. 3D lock was always available with up to 11 birds in view many many times above 60 degrees North Latitude. The accompanying table shows one particular set of data obtained at 0820 hrs local time, 0620 UTC. The farthest north latitude when operation was obtained was 71-10.49, with 9 birds locked on and tracked.

Our itinerary took us virtually to the Russian border, with Murmanske not far away.

On the return trip at our repassing across the Arctic Circle, the marker on the adjacent island was found to be about one mile south of 66-33 North Latitude where it belonged. The Captain laughed and said that it was placed for the convenience of the cruise ships in a place where close by passage was safe and that my GPS location was about right!!

For the flight home, when the Captain was again asked for permission, the First Officer commented that I probably wouldn’t get satisfactory operation. He was dead wrong. I was able to track the flight with the limited visibility of the aircraft window about 90% of the time. I watched Iceland and Labrador come and go.

As I left the plane I told him that I had no problem with operation. He showed surprise as I was pushed out the door in the crush.

 All in all a very successful and satisfying baptism of the new (to me) GM100.


                                Site Data 

                                (Data taken on the top deck,  GM 100 AA batteries)


                Location  70-59.327N        SOG 16.1 KN         Time  0820 Local

                                .025-09.041 E        COG  261 Mag                 0620 UTC

                                EPE  62 ft                               3D Lock


                Sat#        Elevation               Azimuth                 Status SNR       

                   1           29                            291                          Tracking 34

                   4           42                            76                            T                             40 

                   5           57                            149                          T                             41 

                   6           20                            220                          T                             39 

                   8           32                            187                          T                             34 

                  14          21                            353                          T                             32 

                ..16          25                            24                            T                             35 

                  24          35                            128                          T                             40 

                  25          33                           302                          T                             33 

                  29          15                            236                          T                             33 

                  30          61                            234                          T                             39 


                                Tracking 11 out of 11 satellites visible

Al Perrins

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