[aprssig] A Proposal for the Continuation of APRS

Jonathan Delaney kb3osp at gmail.com
Mon Feb 14 20:01:32 EST 2022

Theoretically any number of protocols could be sent at the same time provided that the number of protocols does not exceed the bandwidth of 16kHz (normal FM transmit bandwidth). But nothing can happen with a second protocol until the first is taken care of and proper documentation is done then a second can't be formed. 


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On Feb 14, 2022, 19:37, at 19:37, 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.
>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
>>>> with collisions and hidden transmitters without making it worse
>>>> 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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