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[aprssig] An amusing aside (Text Pagers)

Matti Aarnio oh2mqk at sral.fi
Thu Jan 28 22:27:53 UTC 2010


On Thu, Jan 28, 2010 at 01:02:45PM -0500, Wes Johnston, AI4PX wrote:
> 
> Can we reprogram the CAP code to something that is predictable and derived
> from our callsigns?  I just checked the numeric pager on my hip and it seems
> to have a 9 digit cap code.  What would be nice would be to have a 12 digit
> or more cap code.... if so, we could use pairs of digits to represent ascii
> codes for our call letters.

Maybe, but the CAP code may not be related on the real addressing mode
of the pager.  POCSAG had 21 bit device address field, and commercially
the pager numbers were mapped to these POCSAC RIC codes at "pager center"
server.

(The CAP code is FLEX's version of POCSAG's RIC, value space is perhaps
different..)

> A= ascii 65
> I = ascii 73
> 4 = 52
> P = 80
> X = 88
> 
> So my cap code would be 00 65 73 52 80 88.  This is the same trick we use on
> TCP mac addresses in the AMPR domain, right?

You are looking for an algorithm that does this above mentioned translation
algorithmically without centrally coordinated database.

On the other hand, reliance on APRS-IS implies network internet connectivity,
and on a possibility to periodically download a fresh copy of such mapping
dataset.   Furthermore, there could be regional server supplying these
callsign to address code mappings, and other necessary coordination services.

What those services would be?  No idea, but if somebody can really supply
pagers receiving on ham bands, I am pretty confident we can come up with
datastream generation methods for them, and generate ideas on what those
coordination services would be.

If all that pager hardware has gone the way of all e-waste, there is not
much incentive on creating programs using them, especially as at these
here parts of the world, pagers died away several years ago.

> This sounds to me like we'd need to do this on another frequency away
> from the normal aprs ops.  I strongly suspect that it will be far easier
> to find 70cm pagers than 2m alpha pagers.

Definitely on different frequency.  70cm ISM frequencies are free of
ham radio traffic for obvious reasons, there could be free freq slot
there somewhere...   High placed powerful transmitters reach better the
low placed receivers, than low placed weak transmitters reach the
high-placed receivers.  Add on it the radio noise power that a low
placed pager receives vs. high-placed digipeater receiver.

> Wes

73 de Matti, OH2MQK



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