At 10:34 AM 9/29/96 -0700, Steve Schear wrote:
I used to be an avid RC modeler and have contemplated organizing an on-going amateur cruise missile contest. The object would be to accurately deliver various payload weights over courses of various terrain and distances (perhaps out to a hundred miles or more in the case of Giant Scale craft). Judging would be based on speed, stealth (noise, IR emissions and radar cross section) and accuracy.
Craft are free to use any navigational technology, but must be autonomous from launch to delivery. To aid navigation I was considering the design of a substitute differential GPS beacon functionally interchangable with those offered by the USCG. My device would work on a different frequency, possibly using very wideband direct sequence spread spectrum (for low probability of intercept/detection) and be actuated by the missile as it neared the target in order to refine its position.
The data standard for differential corrections is called "RTCM-104", and it's the signal you input into differential-capable GPS receivers. Boxes to generate RTCM-104 are probably relatively cheap, primarily needing a multi-channel GPS receiver and another processor for coding. Differential corrections can, of course, be transmitted on any frequency you'd like, including frequency-hopping if you're really concerned about intercept. (which you won't be...) Incidentally, GPS receivers are getting REALLY small these days, particularly for just the module-level products. A size like about 1 inch by 2-inches is pretty close to state-of-the-art. Power consumption is about 3/4 watt. Jim Bell jimbell@pacifier.com