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[aprssig] APRS on all Radios!!!!

Robert Bruninga bruninga at usna.edu
Sun Aug 17 05:01:13 UTC 2008


>> 48 bits of data can get you a position...
> 
> Scott, looks like you can have a new project.  
> Make a dongle for these P25 radios that takes 
> GPS input and sends out the right bits for APRS.  
> Lets define the format... Howabout something


Woahaaa!  Make it for ALL radios TOO.!!!!

Make it encode data at say XX Hz (in PL range).  Plug this into
ANY FM radio that has an external TX modulation input (that goes
down to XX Hz).  Then instead of PL, this station sends his XX
Hz data..

Make a RECEIVE dongle tht plugs into the REPEATER receiver (on
the discriminator) so it can decode the XX Hz data.  This dongle
then converts the data to APRS format as I described below.
Bingo.  A great CLUB project.  One  RX dongle at the repeater,
and dongles for every member who wants to be tracked.

See the APRS Touctone spec.  This is the samething, but is
continuous, and does not need the operator to do anything but
key his mic to be seen in APRS.. (with Frequency, call, date,
time, repeater, position, etc...)

Wow, so much to do, so little time...  Bob, Wb4APR

> like:
> 
> CCCCCC-SS>PX:AAAAGGGG,CC,SS,AAA/$,freetext up to 17 bytes (or
> more)
> 
> PX is some code for your dongle that does this process for P25
radios
> Where AAAAGGGG are the 8 bytes of lat/long
> CC and SS are course and speed
> AAA is the altitude
> /$ is the symbol and
> Freetext can go on the end.
> But free text can also contain FREQ if it is available
> 
> But in general, the FREQ will be added when this is received
at
> the Repeater site and conerted to APRS.  The repeater that
> receievd this and does the conversion KNOWS what freq it is
on.
> 
> THen you also have to make the dongle at the repeater to
convert
> this to APRS.  I suggest this standard conversion.
> 
>
CCCCCC-SS>AP25xxx,WIDE2-2:!DDMM.mmN/DDDMM.mmW$CSE/SPD/FFF.FFFMHz
> 17-bytes-of-free-text!DAO!
> 
> Notice that FFF.FFFMHz is inserted by the digi.
> !DAO! Is on the end so that it does not mess up text displayed
> on all existing radios.  Notice that if there is no GPS data
in
> the user uplink data, then the repeater dongle inserts its own
> position, and a P25 generic SYMBOL with a randomised LATITUDE
to
> make all users on this repeater appear as a list on all APRS
> maps.  Seee details on this process on the
> www.aprs.org/aprstt.html web page.
> 
> By doing it this way, evevn if the P25 radio user does not use
> GPS, he still appears in APRS with a frequency and location...
> If he has  your dongle.
> 
> I have no idea how many P25 users there are...  But we need to
> get all radios on APRS eventually...
> 
> Bob, WB4APR
> 
> > 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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> > > https://lists.tapr.org/cgi-bin/mailman/listinfo/aprssig
> > > 
> > > 
> > 
> > 
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> 
> 
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