[MRCA] The backpack GPS project

[Ray Fantini]

Everyone agrees that it's a fun box to have something that weighs thirty pounds that's strapped to a allice frame to do what the smallest I phone will do only better, but if you don't understand the attraction to the use of obsolete and arcane technology you should not be reading this in the first place.
So far I have determined that the backpack system is a Magnavox MX 4400 and may be one of the earliest systems out there. Attached is a copy of the sales brochure from back in 1987, the backpack can be seen on page 5
Test with the system have provided some information, first when the system powers up it wants to know what "Plan" you want to run. There is a list of about twenty different navigation plans for locations throughout the world along with several cryptic modes that I do not understand. Loading the CONUS US plan results in just a message that the antenna appears to be obstructed after a while when it cannot find any satellites. One of the other plans, I cant remember the name right now has somewhat the same results but did notice that after ten or fifteen minutes the clock function sets itself correctly so assume something's getting thru.
Going to assume that this is not just the old NAVSTAR VHF/UHF system but do not know if its got the smarts to decode modern L1 band data or not? The antenna definitely looks like a L1 antenna but not certain about the software. Unfortunately for some weird reason on this version they eliminated the SATS and STAT buttons. The buttons are there but not labeled. Assume this set had a limited version of firmware?  All other buttons and otherwise its identical to the commercial 4400 or 5400 receivers. Will go thru when I have time and write down all the different navigation plans that are offered and see if that has any useful information.

Ray F/KA3EKH


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