[aprssig] Error checking within APRS packets

Guido Trentalancia iz6rdb at trentalancia.com
Mon Jun 27 12:39:18 EDT 2011

Hello Stephen !

On 27/06/2011 02:49, Stephen H. Smith wrote:
> On 6/26/2011 11:48 AM, Guido Trentalancia wrote:
>> It should still be possible to do it with little risk. As long as 
>> there are no (multiple) interactive connections ongoing, there should 
>> be no need (for anything or anyone) to switch the stream. Or at 
>> least, this is my understanding (consider I do not have such a TNC, 
>> as the Kenwood TM-D710 uses 0x01 by default, and I have never used 
>> that function anyway). And usually for APRS, one TNC is exclusively 
>> devoted to APRS itself.
> Stream switching is very much used exclusively within APRS!

You never stop learning...

I thought it was mostly used for AX.25 in packet radio.

> The Kantronics KPC-9612 and KAM dual-port TNCs contain two separate 
> radio interfaces (modems) that input/output through a single shared 
> RS-232 serial port.  They can also cross-digipeat between the two 
> modems internally.  The vertical "pipe" character and the tilde are 
> used to select between the two sides of either of these two devices.
> The 9612 has been used in mixed 1200 baud/9600 baud networks or as a 
> gateway between users on 144.39 and a backbone on 9600 baud UHF.  For 
> decades, The KAM which operates 300 baud HF on one side and 1200 baud 
> VHF on the other, has been used by nearly all HF-->VHF gateway 
> stations.  The real-time all-US HF, and real-time local-area VHF, 
> displays on my UIview APRS webserver are produced by the two sides of 
> a single KAM.connected to a single serial port on the PC.
> The existence of these two devices is one reason that the pipe symbol 
> and tilde symbol in the APRS symbol chart (that otherwise uses all 
> printable ASCII characters) have been kept unassigned all these 
> decades.   Full APRS symbol set into here on my website:

In any case, it can be configured using the STREAMSW command followed by 
the new character to be used for that purpose.

It should be rather difficult nowadays to find TNCs that cannot be 

> -- 
> Stephen H. Smith    wa8lmf (at) aol.com

Guido IZ6RDB

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