[aprssig] A Proposal for the Continuation of APRS

[Andrew Pavlin]

 That is assuming both channel-sharing protocols use the same modem tones and data link framing (which APRS and OpenTRAC can do). Something like M17 couldn't share the channel because it uses a different modulation and framing scheme, so a Bell 202 tones/HDLC/AX.25 receiver would only recognize the M17 signal as interference (and vice versa).

    On Monday, February 14, 2022, 07:37:44 PM EST, Scott Miller <scott at opentrac.org> wrote:  
 
  Yes, the receiving device wouldn't even know the protocol until it gets the packet and verifies the FCS and checks the protocol ID. Regardless of whether the device is using a SQL/COR signal, VOX, or the modem's carrier detect it's still going to register as being in use. Some digis might be ignoring carrier detect and transmitting over packets, but that's a configuration issue.
 
 Scott
 N1VG
 
 On 2/14/2022 4:14 PM, Greg D wrote:
  
 
 Will stations on the channel that are not dual-mode recognize the "other" traffic as "channel occupied", or just transmit over the top and kill the packet?  That would be my worry, devolving to Aloha utilization levels or worse.
 
 Greg  KO6TH
 
 
 Scott Miller wrote:
  
 

 
 On 2/14/2022 12:55 PM, Andrew Pavlin via aprssig wrote:
  
 
 You can't practically run both protocols on the same RF channel because it wastes channel bandwidth on signals some (single-protocol) stations can't understand. We have enough problems with collisions and hidden transmitters without making it worse with doubled transmissions from the same stations. Plus, there are some digipeaters that can't handle two AX.25 frames back-to-back (i.e., one APRS, one OpenTRAC).  
 I disagree. The added on-air time isn't nearly as bad as a doubling since the modem is already locked and everything. Yes, some digipeaters might not handle it, but you can put the OpenTRAC packet second if that's not your primary protocol and you'll only lose the less important one, and you can work on modernizing the network as you go.
 
 Scott
 N1VG
 
 
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