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
___
Sent via AMSAT-BB@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
