[aprssig] First digi versus last digi?

Steve Dimse steve at dimse.com
Wed Jan 21 15:46:25 CST 2015


On Jan 20, 2015, at 3:49 PM, Robert Bruninga <bruninga at usna.edu> wrote:
> 
> Use any timer/pic porocessor/tracker and simply transmit a short STATUS text once every 10 minutes.
> APRS.FI and/or FINDU.COM plot the location of this first heard-no-posit-beacon and plots it as a “VICININTY” plot showing the nearest digipeater that heard it.  FINDU does this now, I am not sure about APRS.FI.
>  
> This gives you a plot anywhere in the country where that tracker has been (to the nearest 10 miles or so).  And at one packet every 10 minutes at  5 Watt output, then the average power is 0.01W or at 7 volts (6 cells) at 1.4 mA which should last 2000 hours on a AA alkaline cell or about 3 months.
>  
If you aren't aware the smart phone revolution has resulted in some amazing improvements in GPS. For $13 you can get the tiny ublox NEO6-M breakout board+antenna: 3.3 volts at 50 mA, with a massively parallel correlator yielding a 27 second cold start time. If you run it every 10 minutes you stay in the 3 second warm start time window (but you do need an occasional longer run to update the almanac). This thing takes about 40 seconds to lock up from a cold start in my house which has a metal roof. None of my Garmins or Motorolas will lock up without an outside antenna.

With this you can get a lot of fixes from 6 AA cells, if you really need to power it with small batteries. I'd rather go that way than rely upon vicinity tracking.

Steve K4HG


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