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Re: tracking through APRS

Hi Bob,

Thank you for your answer. 

>From your answer I understand that I'm well within an acceptable margin
of error for a 30 mile radius. I will download APRSdata and work with

I already have a Linux based Info Server (DIGI_NED, Tiny Web Pages)
running in my area, and I would like to extend the services with
tracking information. The intention of the software I'm writing is that
it serves a relative small area rather than to serve a larger region. 


Bob Bruninga wrote:
> All APRS stations including the D700
> mobile or D7 HT know where they are, they all compute and display the
> actual AZIMUTH and DISTANCE to the satellite unique to them.
> Thus, each radio already has precise and unique azimuth data, including
> an arrow on the front panel pointing in that direction!  There is also
> no need for elevation data Since most LEO satellits are about the same
> height.  THus there is a one-to-one correlation between RANGE and
> ELEVATION ANGLE.  If the satellite gets to within 800 mi, then it is about
> 45 degrees up.  If it is further than 1200, then it is around 30 deg or
> less.  And so forth.
> This way, only one APRSdata needs to be running in each major region and
> it provides good updates to every HT and mobile within several hundred
> miles.
> > I tried to get an answer using tracking software....
> No need to do that.  Just look at the geometry.  If your position says
> the satelite is at 60 deg up to your west, then someone that is about
> 300 miles west of you will see it overhead (90 deg) etc..
> > Any feedback is appreciated.
> So, I chose to let the users HT and Mobile compute the AZ and DISTANCE
> instead of burdening the channel with the same data that is only good for
> your station.  Instead, APRSdata.exe uses the available 20 free characters
> to transmit the satellite UPLINK and DOWNLINK frequencies and
> instantaneous Doppler.
> Thus the HT or mobile user SEES ON HIS RADIO FRONT PANEL the following
> data:
>    AZimuth and distance
>    Frequency of the UPLINK and current doppler
>    Frequency of the DOWNLINK and current doppler
> And that is ALL he needs.  He just tunes to those freqs, works the
> satellite and then goes back to monitoring APRS on 144.39 until his HT
> ALSERTS him to the next pass.
> Also, APRSdata sends out a single packet in the DX Cluster Spot format
> that the HT and MOBILE capture once every 10 minutes.  This single packet
> contains the SCHEDULE of all ssatellites that will be in view in the next
> 80 minutes.  THus an HT or MOBILE user never needs a computer, laptop or
> KEPS or list of freqs or anything.  His radio has everything he needs to
> know about all satellties both IN VIEW and ANTICIPATED in the next 80
> minutes.
> I call it TINY WEB PAGES that are "pushed" to every radio on 144.39 in the
> north american continent.  If there is not someone running APRSdata in
> yoru area, then just download it and run it on an old DOS machine in the
> corner to serve your fellow hams...
> P.S. APRSdata also can transmit a single ONE-LINE-ELEMENT once an hour
> 24 hours a day so that after  monitroing the APRS channel for only about
> 36 hours, your computer will be updated with the latest elements...
> continuously if you want...
> de WB4APR, Bob
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