GPS World, September 2013

EXPERT ADVICE would be chosen to create the designs Then one of the two would be selected to actually implement Phase 1 of GPS After the first round down select we were now playing in the big leagues GDE Magnavox against Philco TRW The Philco leader Jim Spilker and our guru Charlie Cahn had to work together along with Rockwell engineers to define a common signal for GPS The product of their work is still in use as it was defined then at least for the civil C A GPS signal There were tradeoffs and compromises The length of the short code was a contentious issue TRW had built a 512 bit correlator and Philco pushed that for the C A code Cahn wanted 2048 bits to minimize inter satellite signal interference They compromised on 1024 bits Charlie wanted a serially transmitted short code long code for the military signal to enable long code acquisition a technique we had used in all our modems But Spilker pushed for the codes to be transmitted in phase quadrature a more elegant solution that prevailed The need for a short code arose because the receiver could not acquire the long military signal unless it knew time to microseconds accuracy The military code was very very long By first acquiring the short repetitive C A signal the receiver could read its data and determine time close enough to make a long code acquisition search practical The GDE Magnavox team won the Phase 1 contract and we were developing the first military and civil GPS user equipment UE Our Phase 1 UE contract included quantities of a 4 channel high dynamics set for the F 4 fighter aircraft a 2 channel aircraft set for the bigger and slower C 141 and helicopters a manpack and a civil aircraft set that looked like a TACAN and used only the C A GPS signal The three aircraft sets were called the X set Y set and Z set respectively Before long Col Brad Parkinson director of the Joint Program Office decided that there should also be a competitive high dynamics set and another manpack and awarded a contract to Texas Instruments The USAF avionics laboratory wanted a piece of the GPS action so it awarded a what it called a high technology GPS UE contract to Rockwell Collins For various reasons many not of its own making Collins eventually became the number one supplier of military GPS UE long after Magnavox faded from the scene Hughes and then Raytheon eventually acquired the Magnavox GPS crew where some of my former colleagues still work today The Collins unit flew in the C 141 Our X set flew in a pod under the F 4 The complement of equipment GPS receiver navigation computer power supply and so on was too big to be installed into the aircraft so it was housed in the pod Building the Crew To staff the contract required hiring many new engineers We scoured our competitors and prior employers that had people experienced in the needed hardware and software disciplines and were able to create a crew that went on to become major contributors to GPS developments for decades Some started their own GPS companies like Min Kao who with Garry Burrel of King radio later became the MIN and GAR in GARMIN Another GPS company started by Magnavox people is CAST Navigation a GPS simulator manufacturer The Magnavox Marine Division developed commercial Transit receiver and integrated shipboard navigation systems and survey systems Later on it pioneered GPS based marine navigation systems and eventually split off into another company called Navcom formed by Jim Litton which later became part of John Deere Several notable GPS experts from that Magnavox cadre like Tom Stansell Ron Hatch still with Navcom and Jerry Knight are actively consulting today So with all modesty I have to say that I too was part of that original group who can claim some degree of fatherhood for GPS user equipment and receivers Over the next several years I became an ambassador for GPS traveling the world particularly to visit potential military GPS users in NATO and at other allies In the late 1970s Magnavox and Collins were awarded the Phase 2 userequipment developments About a year before the production contract was awarded to Collins I had left Magnavox to join Interstate Electronics IEC now a major part of L 3 Communications to lead its efforts to become a military GPS user equipment supplier IEC had a unique technology for tracking submarine launched ballistic missiles using a GPS translator tracking system We succeeded in applying it to the DOD test ranges and for Trident missile tracking and submarine navigation In my later years there we eventually miniaturized the GPS receiver to the point where it could be applied to guiding missiles and projectiles After nine years at IEC I decided to go out on my own as a consultant and formed Global Systems and Marketing Inc For the next 20 years I worked on various assignments from most of the major GPS companies and several small businesses that were trying to find a position in the GPS market I also participated as an expert witness in many legal cases involving GPS from patent disputes to accident reconstruction to parolee tracking Looking back now from the beginning of my retirement I can obviously say Ive learned a lot Two things stick out in my mind Never believe the schedule and budget anyone offers up because new developments will likely take longer and cost more than originally estimated When you stop being better you stop being good I know the future holds more miraculous applications of GNSS technology because of all the brilliant innovative people working in the field that I have met and those that I havent met but have read about in places like GPS World You are all very fortunate to be part of what I call the most important dual use system after the Internet ever invented LEN JACOBSON is a retired GPS consultant having worked in the field since 1968 He is still active in the Institute of Navigation having been Western regional vice president twice and held leadership roles in several of its conferences He lives in Long Beach California Visit his site at www lenjacobson com GPS World September 2013 www gpsworld com 10