[aprssig] Failed APRS?

Rick Green rtg at aapsc.com
Wed Jan 21 22:50:54 EST 2009

On Wed, 21 Jan 2009, Robert Bruninga wrote:

>> We need to develop as well a convention
>> for the description of the preferred,
>> and possibly multiple, mode/frequency/
>> address tuples for possible direct
>> communication.
> It is defined in www.aprs.org/info/freqspec.txt
   That's good as far as it goes, but it addresses only voice 
communications.  It does not address any of the other modes amateurs may 

>> Only when we have a standard for the
>> broadcast dissemination of a 'link'
>> to a direct communication channel,
>> can we proceed to develop auto-QSY
>> software for our frequency-agile mobile rigs.
> We have had everything we need since about 2001.  We just need
> to glue the pieces together:
> 1) APRS is the local/global signaling channel

   No, APRS is a *local* signalling channel.  Beyond one hop, it's for 
broadcast information only, and on a global scale, it's dependent on the 

> 2) Echolink/IRLP  is the global VOIP link
> 3) APRS knows where caller and callee are located
   No, APRS 'knows' nothing.  An APRS user might glean this by mining the 
datastream, but the APRS system itself is essentially stateless.
> 4) APRS knows where the Echolink/IRLP nodes are
> 5) APRS now has a standard QSY Frequency format
   ...for VHF/UHF FM modes only.

> 6) All we need is a simple AVRS engine somewhere in the APRS-IS
> to monitor for and end-to-end contact request, and then respond
> with the auto-qsy message to both end parties telling them the
> FREQ and NODE numbers, and setting up the link.
   And how will this 'auto-qsy' message be delivered?  My intention with 
this auto-qsy proposal is to eliminate the point-to-point message traffic 
on the APRS broadcast channel.  I also don't like the dependence on a 
third-party potential single-point-of-failure.

   I'd like to see something that works more like this:

   1) You see a broadcast packet on your APRS display.  The packet has an 
'operator present' flag set, and listening freq/mode/address info is 
   2) You decide to send the station a personal greeting, and compose it 
using the facilities of your APRS display.
   3) When you hit send, your APRS display will QSY your radio to the 
intended destination's listening frequency, send the message, await an 
ACK, and return to the APRS broadcast frequency.  Or possibly, if you're 
well endowed, the message traffic could be handled by a second tranceiver 
while normal APRS reception/display continues.

   I see many pitfalls in trying to implement this for anything beyond 
simplex range.  What we really need is an effective route discovery 
algorithm, and a routed protocol for SMS delivery.

Rick Green, N8BJX

"Those who would give up essential Liberty, to purchase a little
temporary Safety, deserve neither Liberty nor Safety."
                                   -Benjamin Franklin

"As for our common defense, we reject as false the choice between our
safety and our ideals."
                                -President Barack Obama 20 Jan 2009

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