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[aprssig] Project-25 for amateur radio

Scott Miller scott at opentrac.org
Sat Aug 16 16:51:17 UTC 2008


48 bits of data can get you a position with ~2 meter resolution 
(40,000,000 meters around the equator / 2^24 = 2.38 meters longitude 
resolution).  36 bits can represent a 6-character, 6-bit callsign. 
Seems like even accounting for some overhead, a 1.5 or 2 second 
transmission would be plenty to get a basic position out.

Scott
N1VG

John Habbinga wrote:
> Bob, there is a low-speed data mode transmitted along with digitized
> voice on Project 25.  However, it passes data at 88.9 bit/s.  As far
> as I know, there are no applications that has made use of this
> feature.  I doubt that it would be very practical to use "APRS over
> P25," but I could be wrong.
> 
> On Fri, Aug 15, 2008 at 3:38 PM, Robert Bruninga <bruninga at usna.edu> wrote:
>> I noticed the QST article on Project 25 using digital voice on
>> repeaters.
>>
>> I noticed a sentence about simple text transfer. And intended to
>> bring the article to work with me for noon time reading, but
>> forgot it.
>>
>> If the radios are capable of digitally exchanging callsigns,
>> then there is no reason why they cannot appear on APRS just like
>> DTMF users.  SO if anyone can point me to a point of contact
>> within that project group, I'd like to invite them to consider
>> joining the global APRS system too.
>>
>> See http://www.ew.usna.edu/~bruninga/aprstt.html
>>
>> Bob, WB4APR
> 
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