[aprssig] Easy Predicting GO-32 for the mobile!

gerheim at cox.net gerheim at cox.net
Sat Oct 13 13:51:02 CDT 2007

I think I have it.  It's on 145.825 at the moment.  I'll switch radios for the evening pass of GO-32.  (Different com ports).  

Let's see what comes down!!!

The Satgate call is K1QN-2.  Locator is FN41di, which doesn't cover much dry land outside of New England.  

---- Robert Bruninga <bruninga at usna.edu> wrote: 
> I've been trying to come up with an easy GO-32 pass-time
> predictor for the mobile.  This morning I got it!  The Ground
> track of GO-32 repeats every 10 days!
> So All you need on your dash board is this strip of paper.
> Day1 Day2 Day3 Day4 Day5 Day6 Day7 Day8 Day9 Day1
> ---- ---- ---- ---- ---- ---- ---- ---- ---- ----
> 0930 0910 1025 1005 0940 0920 1040 1015 0950 0930
>      1050                1055
> 2050 2030 2005 2125 2100 2040 2015 2135 2110 2050
>      2210 2145                2155
> For example, today is Day3 in Wash DC.
> If you print these in fixed font, it will show you the pass
> times for any day and time zone and location, as long as you
> know what day sequence to be on in your area.  And we can have
> GO-32 send down a table-of-days in its bulletins!  So if you
> ever hear GO32 once, then you will have all you need for
> tracking for the next few months or so for your area!
> Initially, I assumed this table would be only for Washington DC
> (77 deg Longitude) and 40 deg latitude where I calculated it.
> But it should also apply anywhere at this longitude north or
> south and be off by less than 5 minutes or so. 
> Then I thought we would need a different one for every 5 degrees
> of longitude... But then realized that just as the pattern
> repeats every 10 days in time, it also repeats incrementally in
> longitude!  Since the longitude increment of GO-32 is about 26
> degrees, that means these multiples of 26 degrees from
> Washington DC will have the same pattern on the same day as we
> do.  And that every 2.6 degrees in between will have an
> additional day offset from ours. 
> Wow, it can't get any simpler than that for mobiles to know when
> to use their rigs on GO-32 when traveling in wilderness areas.
> A similar table could be predicted for ECHO (AO-51) maybe.
> ELEVATION ANGLE:  To keep the chart simple, I did not include
> max elevations, but that can be added in the final version.  It
> is also easy to infer.  The days with double passes are near 30
> degrees each (barely detectible by the mobile)  The days midway
> between these lowest peak passes are the highest elevations (75
> or more degrees).  And you can interpolate inbetween these.
> UPLINKS!  The above table gives you only the BEST pass of the
> day for your location (passes above 30 degrees).  This is the
> pass where you can expecet to receive the GO32 downlink on your
> mobile whip antenna.  HOWEVER, every day, there is a pass
> exactly 100 minutes before and after each of those passes too.
> So now you have 6 chances a day to report your position in the
> wilderness and 2 chances a day to receive any APRS message
> traffic.
> Happy wilderness traveling!
> (Oh, and of course, make sure there is someone in your footprint
> that is SATgating your data into the APRS system so that your
> position and status and any emails get delivered.)...
> Bob, WB4APR
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-Al Gerheim

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