Folks > 1 - rotator control in a moving vehicle to keep a small yagi such as an > Arrow pointed at the APRS signal. > > 2 - antenna parking based on data from a home WX station such as those > commonly beaconing on APRS systems.
FWIW, I did exactly that many moons ago back in 2003 when AO-40 was still with us, although it was more of a working prototype than something you'd want to let all and sundry peruse over. http://www.g6lvb.com/images/AO40Mobile.jpg This was based on a GPS feeding into a PC that corrected the co-ordinates in real time and fed them to an LVB Tracker, hooking up to a pan and tilt camera mount. Since then, in 2005, the LVB Tracker 2 was developed, and that can act autonomously and take in real time GPS parameters for both position and date and time correction, although I must stress that this is not a production strength unit. The LVB Tracker 2 was developed at about the same time as the SDX back in 2005. When I presented separate papers for the Tracker 2 and the SDX at the AMSAT-UK Colloquium, there was a lot of interest in the SDX, but almost none in the Tracker 2, so further development waned I'm afraid. I worked with Gould Smith on it again quite a bit at the beginning of 2008 (see below), but I still don't believe it's really ready for prime time, although should some kind soul come up and offer to spend time developing it further I'd be delighted! It took a lot of time and effort to get the Tracker 2 to where it is today, more so than the Tracker 1: the Tracker 2 firmware is five times the size of that in the Tracker 1. Back in 2005, there was a real limit on what you could a achieve in a tiny 28 pin device as well as the limitations of compilers at that time. The Tracker 2 certainly took to the extreme what you could achieve with the limited ROM and particularly RAM available at that time on such a device. It reminded me of the days when you used all manner of means to squeeze that last byte out of your memory map. The Tracker 2 has two redeeming features. Firstly, it can operate as a handheld device with an integrated GPS, but since then the iPhone has come along! Secondly, Tracker 2 will work autonomously. The bad news is that if you run a desktop Tracker 2 based on the original Tracker 1 PCB without a GPS, with there being no RTC clock, you have to reset the date and time manually each time you switched it on, so that's a bit of a drawback unless you leave it on all the time. Even then, we found that the crystals drift the RTC rather too much for our liking. I think if time permitted, redesigning the LVB Tracker 2 hardware with a new PCB from scratch would be preferable, supporting a proper battery backed RTC. FWIW, I am often asked about the choice of compiler for the LVB Tracker. Some history: the early choice of the BKND compilers for the LVB Tracker was because, way back when, they offered floating point arithmetic for a reasonable price unlike other competitive offerings, although you're heavily restricted as to the complexity of your code, so you have to manually code around those restrictions. Since then, other more heavyweight compilers have come along, in particular Microchip's own offerings for the PIC18 and above. Rewriting the code for those compilers would be 'interesting'(!) for someone with some time on their hands, and some $$$ to purchase the compiler. But, some good news. Thanks to Gould Smith's good work testing my code back in early 2008, I do have some significantly updated Tracker 2 code since 2005, but please bear in mind this is for experimentation purposes, and current work commitments preclude me from opening this puppy up for now, but please feel free to do so yourself! See below... 18F2620 programming software: http://www.g6lvb.com/Articles/LVBTracker2/PicProg2.exe Hex file: http://www.g6lvb.com/Articles/LVBTracker2/2620test20d.hex Sources: http://www.g6lvb.com/Articles/LVBTracker2/2620test_2_0d_001.zip By the way, while researching the content here, I came across some interesting LVB Tracker development history shots are here (if you're into that kind of thing): http://www.g6lvb.com/images/lvbtracker1.JPG http://www.g6lvb.com/images/lvbtracker2.JPG http://www.g6lvb.com/images/lvbtracker3.JPG http://www.g6lvb.com/images/lvbtracker4.JPG http://www.g6lvb.com/images/lvbtracker5.JPG http://www.g6lvb.com/images/lvbtracker6.JPG http://www.g6lvb.com/images/lvbtracker7.JPG Judging by the number of PCBs that have been made, I believe that there are now in excess of 1,000 LVB Trackers out there, although how many are operational and how many are sitting in pieces waiting for a rainy day I don't know! 73, Howard G6LVB _______________________________________________ Sent via amsat...@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
