[ML-Hams] Android + APRS

Mon Mar 21 19:44:11 CDT 2016

I saw an old AX.25 TNC ad the shop. I don't know if it works.

I had an AX.25 node setup. That mode is pretty dead in this area.

TCP/IP doesn't work very well over it. It's an old protocol and they are
almost opposites in their technical approach.

On Mon, Mar 21, 2016 at 6:46 PM, Kris Kirby <kris at catonic.us> wrote:

> On Mon, 21 Mar 2016, Jeff Cotten wrote:
> > This looks awesome, I want one.
> >
> > Products like these will help address the issue of attracting young
> > blood to the HAM hobby.  A further improvement would be reducing the
> > learning curve by explaining what KISS, APRS, and TNC is.  Newcomers
> > have no idea why they should be interested in whatever those acronyms
> > mean.  I only got a taste of what APRS was last night watching a
> > youtube video of some guy running a telnet sessions over his radio at
> > 1200 baud:  https://www.youtube.com/watch?v=f-Be8e2tclU
>
> A TNC is a Terminal Node Controller, or basically an intelligent message
> processor (IMP), an interface box that allows a user on a dumb terminal
> to communicate with other users through a transmission medium with IMPs
> at both ends. The TNC contains a modem, packet buffer, and interface
> control logic to control a radio transmitter, modulate the transmitter,
> and decode the audio from the receiver.
>
> https://en.wikipedia.org/wiki/Interface_Message_Processor
> https://en.wikipedia.org/wiki/Terminal_node_controller
> https://en.wikipedia.org/wiki/Packet_radio
>
> TAPR gave birth to the TNC:
> https://www.tapr.org/packetradio.html
> https://www.tapr.org/kits_119.html
>
> KISS is a TNC specific serial protocol:
> https://en.wikipedia.org/wiki/KISS_%28TNC%29
>
> KISS is designed to place the received packets on the serial bus as
> quickly as possible with as little extraneous information as possible,
> and to do the same on transmit.
>
> eXtended KISS (XKISS) is a multi-dropped (like RS-485) version of KISS
> that allows for attaching multiple devices (TNCs or computers) to a
> shared serial bus. G8BPQ's node stack supports this, and the Kantronics
> KPC-9612 supports this as well, providing two "distinct" virtual TNCs
> when used in XKISS or KISS mode.
>
> There are hardware TNCs, originally based on RS232 serial
> communications. TNCs have been made that used the Zilog Z80 (TAPR TNC2)
> and Motorola 68HC11 (Kantronics KPC-series). There are now software
> TNCs, for both Windows and Linux which use sound cards.
>
> The "over-the-air" protocol is called AX.25, which is an extension of
> the X.25 network stack:
> http://tldp.org/HOWTO/AX25-HOWTO/x61.html
> https://en.wikipedia.org/wiki/AX.25
>
> There are also node stacks, both hardware (TheNet, ROSE) and
> software such as G8BPQ, JNOS, TNOS:
> http://www.cantab.net/users/john.wiseman/Documents/
> http://kf8kk.com/packet/jnos-linux/thenet-ops-1.htm
> https://www.tapr.org/pdf/DCC1993-ImprovedTNCinterconnections-N2IRZ.pdf
>
> http://kf8kk.com/packet/jnos-linux/jnos-ops-1.htm
> http://www.langelaar.net/jnos2/
> http://www.linux-ax25.org/wiki/TNOS
>
> AGWPE works as both a sound card software TNC and a node stack:
> http://www.sv2agw.com/ham/agwpe.htm
>
> There is/was TCP/IP stuff, but it's not used with APRS:
> https://en.wikipedia.org/wiki/AMPRNet
> http://www.ampr.org/
> http://wiki.ampr.org/wiki/Main_Page
>
> Tim, N8DEU, may be a better source for what APRS and packet are than
> myself. I tend to look at things as what you can do with them, as
> opposed to what they are said to be. APRS is many things, part network,
> part application, part message-passing.
>
> One analogy would be a single-frequency network composed of simplex,
> half-duplex repeaters which repeat something like UDP frames of
> information and limited broadcast domain control logic combined with a
> little bit of intelligent message routing.
>
> But 1200 bps half-duplex is slower than it appears to be, however there
> is compression involved in some APRS packets.
>
> Over-arching project itself:
> https://en.wikipedia.org/wiki/Automatic_Packet_Reporting_System
> http://www.aprs.org/
>
> "Backbone" / "Internet Infrastructure": http://www.aprs-is.net/
> IGate: http://www.aprs.net/vm/DCC97/internet/
> http://www.findu.com/
>
> Applications:
>  Google Maps + APRS-IS: http://aprs.fi/
>  http://www.findu.com/
>
> Text messaging from internet to APRS:
>  http://www.aprs.org/aprs-messaging.html
>  http://www.findu.com/cgi-bin/entermsg.cgi
>  http://www.aprs-is.net/email.aspx
>  http://aprsisce.wikidot.com/doc:aprs-messaging-explained
>
> Single-frequency networking:
>  https://en.wikipedia.org/wiki/Single-frequency_network
>  http://www.aprs.org/fix14439.html
>  http://www.aprs.org/fixingLA.html
>
> It's also important to point out that there's more than one way to
> modulate a transmitter. 1200 bps APRS relies on the ad-hoc standard of
> Bell 202 modem + commodity two-way radio = signaling inside of the voice
> bandwidth (300 - 3,000 Hz) without equalization or correction.
>
> We have other speeds such as:
>
> 2400 bps is the fastest speed inside the voice bandwidth (for now). This
>  required special modules to go into the TNC, changing jumpers, etc.
> 9600 bps GMSK/GFSK using modified radios or special, standardized ports on
> the radio now.
> 19,200 bps required special radios and/or special TNCs, or serial cards,
>  or mods to TNC and/or radios (replacing IF filters, tapping into the
>  modulator directly).
> 56,000 bps required a special ISA card (PI-2) with a Zilog Z8530 serial
>  processor which natively built X.25 frames and performed synchronous
>  serial communications, as well as the GRAPES modem and modified
>  transverters: http://www.wa4dsy.net/rfmodem.html
>
> And that's just the tip of the iceberg. There are other modes yet to be
> discovered or implemented to maximum the bandwidth of a 0-4KHz audio
> path or 300 - 4,000 Hz audio path.
>
> V.90 or V.92 maximized the bandwidth of what could be obtained in a
> voice-grade audio path at about 33.6KHz, but those modems are encumbered
> by patents. Carrier frequency is 3429 Hz, however. But those modems also
> don't work in half-duplex -- they are full-duplex only.
>
> --
> Kris Kirby, KE4AHR
> Disinformation Architect, Systems Mangler, & Network Mismanager
>
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