[aprssig] A TNC2 (clone) question

[Steve Daniels]

Argent data will program a KISS rom for $5, they will also program a UIDIGI
rom for free to encourage digipeaters. Using a 27C256 rom.

At a  guess they would probably program other digipeater firmware for free.

You need to supply the code you want programmed however.

https://www.argentdata.com/catalog/product_info.php?products_id=24

I have both roms for a tnc2 clone from them

 

Steve Daniels

G6UIM

Torbay Freecycle Moderator

  _____  

From: aprssig-bounces at tapr.org [mailto:aprssig-bounces at tapr.org] On Behalf
Of Stephen H. Smith
Sent: 14 November 2011 17:18
To: TAPR APRS Mailing List
Subject: Re: [aprssig] A TNC2 (clone) question

 

On 11/14/2011 9:24 AM, kc8sfq at mei.net wrote: 


Hi  All:
I have an old MFJ1274 TNC. I'm thinking of putting it, along with a radio
and a gel cell battery, in a waterproof box for use as a temp DIGI for SAR
and similar such field use.

What I know about the MFJ:
1: It won't work with APRSISCE/32 (my fav) since it won't stay in KISS mode.
2: It'll require a new EPROM for extended KISS operation. That's about
$40-50 by the time it's all up and running. There are better and easier ways
to do that for the same money.


Replace the eprom with the last-ever TAPR Release 1.1.9 firmware which has a
perfectly serviceable KISS implementation in it.   





My questions:
1: Will the MFJ1274 support the new n-N paradigm? or will it need to be
addressed by it's specific callsign-SSID? (I know it's been upgraded to at
least 1.2.9 firmware)


Not as-is, with the exception that if all you want it to do is be a
home-style first-hop fill-in digi, then set it's callsign "alias" to
"WIDE1-1" . (The first-hop WIDE1-1 digipeating doesn't depend on the TNC
having  the APRS-centric callsign-changing/substituting capability described
below.)





2: will the MFJ even function as an APRS DIGI? (my understanding is that
there's nothing special about an APRS packet as far as a DIGI is concerned)


But there ARE major differences between classic connected packets and APRS
packets !   

>From the standpoint of the AX.25 protocol used by both "classic" packet and
APRS,  the path settings are the callsign(s) of the station(s) being asked
to relay the packet.  In classic packet, these would be the actual calls of
the stations involved; i.e. you had to know in advance the calls of the
stations involved to get a packet relayed.  In APRS, all stations respond to
the same generic "callsigns" of WIDE1-1, and/or WIDE2-n.    

Current "New Paradigm" APRS depends on digipeaters being able to actually
CHANGE these "callsigns" as packets pass through them -- something classic
packet NEVER did.    APRS digis modify these "calls" as they pass the packet
on, to track and control the number of relay hops.   For example,  WIDE2-2
becomes WIDE2-1 which becomes WIDE2-0 as a packet passes through 3
successive digis.     This handling of callsigns is unique to APRS.      

Many of the new-breed low-cost KISS-only APRS-only TNCs such as TinyTrack 4,
Tracker2, TNC-X, AGW uTNC, etc  CAN do APRS-style digipeating stand-alone.
The ONLY "classic" TNCs able to do this off-the-shelf stand-alone (i.e.
unassisted by computer programs), were the Kantronics KPC3 family TNCs.
PK-232s, TNC2s, etc require a computer program running through a KISS
interface to do modern APRS digipeating. 

You can endow almost any TNC-2 clone, such as your MFJ with this ability by
replacing it's OEM firmare with the freeware UI-Digi firmware that converts
the TNC2 to a dedicated APRS digipeater.  However it becomes STRICTLY a
stand-alone digipeater, and can no longer be used for local transmit/receive
by a an attached PC.   


See the full history and underlying logic of APRS digipeating here on my
website:

"APRS 101"  Explanation of APRS Path Selection & Digipeating 
  http://wa8lmf.net/DigiPaths 

  _____  


--

Stephen H. Smith    wa8lmf (at) aol.com 
=== Now relocated from Pasadena, CA back to 8-land (East Lansing, MI) ===
Skype:        WA8LMF
Home Page:          http://wa8lmf.net

=====  Vista & Win7 Install Issues for UI-View and Precision Mapping =====
    http://wa8lmf.net/aprs/UIview_Notes.htm#VistaWin7

*** HF APRS over PSK63 ***
   http://wa8lmf.net/APRS_PSK63/index.htm






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