Since I had been in-active for quite a number of weeks, of course I first wanted to check if my (70cm) satellite station was still functional. The first step I always take is listening to the stable beacon of HO-68, CW @435.790MHz. My goal is to have the antenna tracked automatically, and frequency PC controlled by HRD. When the result is that I hear the beacon, no doppler shift, I know this first step is taken (means hardware and software incl kepler sets seem to work). Now what next ? Signal strength of that CW beacon is one way to measure my station, another way is looking at RAX-2, which transmits at 437.345 MHz (9k6 FM packets, KISS mode). RAX sends these days each 10 seconds a short burst of data. Using the free decoding SW from the RAX team you can: a) analyze the satellite data yourself b) help the scientific experiments of the university by forwarding the telemetry c) test your own station ! http://rax.engin.umich.edu/?page_id=301 An example is this mornings pass, which had a max elevation of 46 degrees. With my 16 elements DK7ZB (http://pa3guo.com/ant_jun_2011.jpg) my station could hear the satellite starting at 2 degrees elevation, and decode at around 8 degrees. See the table below (decode timestamps from the decoding software) 4 May 2012 07:51:38 GMT (6.2 degrees elevation) 4 May 2012 07:51:49 GMT 4 May 2012 07:52:01 GMT 4 May 2012 07:52:09 GMT 4 May 2012 07:52:19 GMT 4 May 2012 07:52:29 GMT 4 May 2012 07:52:39 GMT 4 May 2012 07:52:50 GMT 4 May 2012 07:53:02 GMT 4 May 2012 07:53:10 GMT 4 May 2012 07:53:20 GMT 4 May 2012 07:53:30 GMT 4 May 2012 07:53:41 GMT 4 May 2012 07:53:51 GMT 4 May 2012 07:54:01 GMT 4 May 2012 07:54:11 GMT 4 May 2012 07:54:21 GMT 4 May 2012 07:54:32 GMT 4 May 2012 07:54:42 GMT 4 May 2012 07:54:52 GMT 4 May 2012 07:55:02 GMT 4 May 2012 07:55:12 GMT 4 May 2012 07:55:22 GMT 4 May 2012 07:55:33 GMT 4 May 2012 07:55:43 GMT 4 May 2012 07:55:53 GMT 4 May 2012 07:56:03 GMT 4 May 2012 07:56:13 GMT 4 May 2012 07:56:24 GMT 4 May 2012 07:56:34 GMT 4 May 2012 07:56:44 GMT 4 May 2012 07:56:54 GMT 4 May 2012 07:57:05 GMT 4 May 2012 07:57:15 GMT 4 May 2012 07:57:25 GMT 4 May 2012 07:57:35 GMT 4 May 2012 07:57:45 GMT 4 May 2012 07:57:55 GMT 4 May 2012 07:58:06 GMT 4 May 2012 07:58:16 GMT 4 May 2012 07:58:26 GMT 4 May 2012 07:58:36 GMT 4 May 2012 07:58:46 GMT (11 degrees) ... 4 May 2012 07:59:48 GMT (5 degrees) So at the end my station stopped decoding at 11 degrees elevation, it picked up a final beacon at 5 degrees. We could define a kind of 'Ground Station Effectiveness' as number of packets decoded (not heared!) between a certain elevation threshold (eg 10 degrees). When no packet would be missed my station would rate now for 100% (at 10 degrees). Or more scientifically: the GS effectiveness of PA3GUO's station is 100% (@10 degrees elevation) All kinds of items can bring this number down from 100% to lets say 80%: - hard mechanical stop of the rotor, forcing a full 360 degrees turn during a pass - interference of other signals/satellite during a pass (at the same frequency) - tumbling of the satellite (antenne pointing to wrong direction) - polarization changes (rotation of the satellite) Well, the above shows that my 1x16 elements (horizontal pol) antenna works fine to support missions like RAX. No need for circular antenna (admitted: other satellite give different results for circular (both better and worse) Just sharing some thoughts, looking forward to your feedback / reflections ! Henk, PA3GUO
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