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Getting Started with Packet radio
KI6ZHD
dranch at trinnet d o t net
12/10/16.1
-------------------------------------------------------------------------------
Index:
------
1. Learning the basics about Packet radio and AX.25
--
2. Deciding on Layer1 - the hardware and software
2.a. Radios: Frequency vs. Speed
2.b TNCs (hardware vs software)
2.c. Picking Packet software (Linux/Win/Mac)
--
3. Setting up a packet station
--
4. What frequencies should you use?
--
5. Making Connected connections
--
6. Understanding Kantronics KNet and KaNet TNC interfaces
--
7. Making UnConnected connections (UNPROTO)
--
8. Next Steps
--
9. FAQ
--
10. Advanced packet - not using AFSK for the mode; use Fldigi
--
20. Errata
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-------------------------------------------------------------------------------
1. Learning the basics about Packet radio and AX.25
There are a few good packet intros out there but one of my favorites
is the Choisser one from WB9LOZ:
http://www.choisser.com/hamradio/packet.html
I also have some other tutorial URLs and other high level descriptions
on my HamPacket documentation:
http://www.trinityos.com/HAM/CentosDigitalModes/hampacketizing-centos.html#5.pkttutor
-------------------------------------------------------------------------------
2. Deciding on Layer1 - The hardware and software
The choice of hardware and software can be a bit complicated as packet
can run on different speeds and frequencies:
2.a. Radios: Frequency vs. Speed
--------------------------------
Radios: Frequency: HF / 300 Baud
If you want to run packet on HF, you need an HF radio and the
appropriate amateur radio operating license. The specific choice
of the radio really isn't as important as you'd expect. Sure,
better the radio, the better the reception but even old tube-type
radios can be made to work.
At HF frequencies, 300baud AFSK packet is as fast as you can go. You
might be thinking that's super slow but that's a *LOT* faster than
almost *all* other HF digital modes modes! It's true! With that
said, 300baud HF packet needs very strong, clear signals to work
well and that doesn't happen all that often. There are newer
versions of 300baud HF packet such as the proprietary SCS Robust
Packet mode but it only works with SCS hardware TNCs (not covered
in this document).
Another approach here is to not use the traditional AFSK mode
and instead, use more modern HF digital modes. See the "Advanced
Packet" section below for more details.
Radios: Frequency: VHF / 1200 BAUD
The most common packet setup is a system running on VHF frequencies
like 2 meters (144MHz) running at 1200BAUD via the AFSK mode. Notice
the term AFSK which stands for Audio Frequency Shift keying. This is
a very simple mechanism and is one of the reasons why these type of
packet systems are easy to setup. Here, almost any 2m handheld (HT)
or mobile FM radio will do. The robustness of the 1200 baud AFSK mode,
inexpensive radio hardware, ease of setup, combined with inexpensive
omni-directional antennas are why this is the most common setup. It's
worth noting that 9600 BAUD using an FSK mode also will work on 2m but
it's not very common.
Radios : Frequency: UHF / 9600 BAUD and faster
The most common 9600 baud packet setups run on UHF frequencies like
70cm / 440MHz and these radios can also support 1200baud packet as well.
9600 BAUD FSK packet is substantially faster than 1200 BAUD packet but
it requires very strong signals to be reliable. Unless you have a good
path to the remote station, you'll need a directional antenna (Yagi, etc)
to make this mode work well. In addition to a good signal, you need
a different type connection to the radio itself. Unlike 1200baud AFSK
packet that uses audio frequencies via basic microphone and speaker
connections, 9600BAUD needs to interface to the radio at the FM
discriminator input/output. This interface provides for flat passband,
which is cleaner and wider interface for data than what a pre/post-
emphasized microphone and speaker connection can offer. Modern 2m/70cm
radios usually have 6-pin "DATA" jack on the back where one of these
pins is for 9600 BAUD / direct discriminator access. If your radio DOESN't
have that connection, you'll have to modify your radio to get access to
it. EVERY radio has a discriminator so it's only a matter of finding
the right connection. Sites like http://mods.dk and other radio sites
will have this information for your radio.
It's also worth mentioning that 19200 baud packet is technically possible
on UHF frequencies. To be useful, the radios in use need to be
of "data grade" which means they can go from TX to RX within 50ms
where as most radios like a Kenwood D710 does that in about 150ms!
Companies like Tekk used to make data radios but there aren't any
of these radios on the new market as far as I know.
2.b TNCS : Hardware vs Software
-------------------------------
When packet radio first came out in the 1980s, it required dedicated
hardware to interface between the radio and the computer. Many of these
TNCs also had features like PBBS systems to leave messages, route packets
via Netrom, etc. all without the computer on. As time has progressed,
many of these TNCs were miniaturized, were optimized to use very little
power, etc. Today, common TNCs available are the Kantronics KPC3+,
Timewave PK96, Coastal Chipworks TNC-X / TNC-Pi, Kenwood D710, etc. You
can still find TNC2-based TNCs like MFJ1270, Kantronics KAMs, and AEA /
Timewave PK232s, etc. In more recent times with computers having decent
quality sound cards, the base TNC function can now be completely executed
in software. Software programs like SV2AGEW's AGWPE for Windows and Tom
Sailor's Soundmodem opened up hardware-less world. Programs like
AGW/PE became full suites with lots of features but they were still pretty
simple at their core. In recent times there is now UZ7HO's Soundmodem for
Windows, WB2OSZ's Direwolf for Linux, Mac, and Windows, and other software
TNCs that are leveraging the power of the computer to improve the weak
decode of packets, etc.
Reliability:
Hardware TNCs offer the simplicity of setting things up once and forgetting
it. That's great and reliability key. Many people still dismiss software /
soundcard based TNCs because of their previous experience of using Microsoft
Windows which would change/reset it's audio levels after patches were
installed, etc. With the pairing with Linux, all of those inconsistent level
issues are gone. There are even tricks with Windows to ensure sound card
audio levels remain stable.
KI6ZHD's recommendation: Direwolf for Linux
You can read more about software TNCs here:
http://www.trinityos.com/HAM/CentosDigitalModes/hampacketizing-centos.html#6.softtnc
If you prefer HW TNCs, I have some cheat sheets for those:
Timewave/AEA PK232: http://www.trinityos.com/HAM/CentosDigitalModes/misc/AEA-PK232-TNC-notes.txt
Kantronics KPC3: http://www.trinityos.com/HAM/CentosDigitalModes/misc/KPC3-TNC-setup.txt
Kenwood D710: http://www.trinityos.com/HAM/CentosDigitalModes/misc/D710-TNC-setup.txt
2.c Picking Packet Software
---------------------------
Back in the hayday of Packet (early 1990s - just before the Internet and
dialup modems starts to become popular), there was a lot of software out
there for packet. Over time, most of the commercial software died off like
PKware, Pakkrat, PKTerm, etc. but there are some still out there.
Linux:
------
My personal focus on HAM radio is with pure Linux. Linux's
biggest strength here is that it supports AX.25 natively in the
OS itself. While there is some packet applications for Linux,
there isn't all that many compared to Windows / DOS. There are BBS programs
like FBB (still maintained), JNOS (still maintained), BPQ32 (still maintained),
TNOS(not sure if it's maintained, and others. As for enduser software, there are
several serial terminal programs to connect to hardware TNCs like Minicom,
Putty, etc. To take advantage of Linux's native AX.25 stack, there is the
program I maintain:
Linpac http://sourceforge.net/projects/linpac/
and there are a few other packet terminal programs. The choices of software really
depend on what you want to do and the platform / operating system you're going to run it on.
For Linux software, check out: http://radio.linux.org.au/?sectpat=packet&ordpat=title
Some of my other favorites are:
UroNode - node software (for sysops)
FBB - BBS software (for sysops)
Windows:
--------
There is a lot more software out there for Packet on Windows but I'm
not all that familar with them. I know some people are very fond of XPware which natively
supports the multi-stream abilities of Kantronics TNCs. Check out
http://www.dxzone.com/catalog/Software/Packet/ for more possibilities.
Mac:
----
There are a few options for AX.25 support on OSX. Sure, you can run a
serial terminal program like iTerm to connect to your HW TNC.
There is the program Multimode which is commercial software for $89 which
natively supports some level of packet but I don't know how good
or extensible it's interface is.
Direwolf - supports the TNC and UI framing for say APRS but there isn't any
classic packet mechanism to interface with. The AX.25 stack included is for
APRS packets only and does not support CONNECTED mode (classic packet).
As such, Direwolf's AGW/PE support does *not* include the connected modes
either.
In recent times, there have been some new alternatives though I
haven't reviewed these in detail:
#AX.25 in JavaScript
https://github.com/echicken/node-ax25
#APRS / AX.25 in GO
https://godoc.org/github.com/dustin/go-aprs
# More APRS / balloon
https://github.com/chrissnell/GoBalloon
#TNC Mux
https://github.com/chrissnell/tnc-server
#Libraries
https://libraries.io/go/github.com%2Fsamuel%2Fgo-dsp%2Fdsp
There are also some Java stacks available as well though I don't
have any experience with them. You can learn more about a few of these
in my Linux doc:
http://www.trinityos.com/HAM/CentosDigitalModes/hampacketizing-centos.html#6.softtnc
-------------------------------------------------------------------------------
3. Setting up a packet station
This is a huge topic in itself on how to connect radios, TNCS/sound cards, etc.
I have many detailed instructions for
Linux (X86 computers here): http://www.trinityos.com/HAM/CentosDigitalModes/hampacketizing-centos.html
Emerging Linux on Raspberry Pi here: http://www.trinityos.com/HAM/Rpi-APRS-project/
If you're interested in running packet on Linux, I recommend a few things
here:
PC hardware / VM:
----------------
- If you'd like to try out a packet and a lot of other HAM radio software on
Linux just from a USB pendrive (doesn't touch your computer's hard drive)
on your X86 bsaed PC or VM, check out:
Andy's HAM Radio ISO - http://sourceforge.net/projects/kb1oiq-andysham/
Ps. I recommend the use of the "Universal USB Installer" windows program
( http://www.pendrivelinux.com/universal-usb-installer-easy-as-1-2-3/ )
or the LiveUSB-creator Linux program ( https://fedorahosted.org/liveusb-creator/ )
to burn images to USB pendrives and also give yourself at least 1GB
of persistant storage (or more) to allow programs to save their configuration
files, add security updates to the Linux side of things, etc. I
personally would recommend to only use 8GB or larger pendrives and
give yourself 4GB of persistant storage.
Raspberry Pi / ARM boards:
--------------------------
- If you'd like to try out a pre-built Linux SD image that includes a very
easy to use AX.25 configuration GUI, check out Hal-Digital:
http://sourceforge.net/projects/haldigital/
- From the maintainer of FBB and FPAC, JeanPail offers an Rpi image as
well:
http://f6bvp.free.fr/AX25_BBS_Node_RaspBerry_Pi_install.html
- There are *many* other outs out there but these are the two I'm familar
with. Let me know of any images out there that you like!
Beyond that, I encourage you to email me, KI6ZHD about specific questions and I'd
be happy to give you my view on on things, give you more URLs to research, etc.
It's just too complicated and vast area of topics to address in one document!
A few final points:
- As they say: Antenna! Antenna! Antenna!
- At all costs, get your antenna outside. You just won't be able to do much
with an antenna that's inside even with a lot of power. It might be a
pain for people in apartments, etc. but it really is required to have
even decent level of performance.
- For 2m only antennas, I've fallen in love with the Diamond CP22E. HRO had
them on sale just a little bit ago for $45 and they are usually $53.
- HT vs Mobile
- 5w only goes so far. A gain antenna will help a LOT but if it's not enough, you
need more power to be heard. You could get an amp for a HT but it starts getting
complicated and I generally recommend to get a mobile radio WAY before getting
an HT amp.
-------------------------------------------------------------------------------
4. What frequencies should you use?
Well, that all depends on where you live. Here in the
South Bay Area of California, there are several high level nodes that can get you
to very far away places. There are also lots of local stations too. Who you
can talk to all depends on your station (the ability of your antenna, your radio,
and power) as well as the remote station's abilities. To hear what's around you,
you need to first determine what are you local packet frequencies. Almost all
regions on the planet have repeater coordinators and frequency coordinators. Some
of the larger areas also have packet coordinators. Here in Northern California,
we have the Northern California Packet Association (NCPA):
Main NCPA page:
http://ncpa.n0ary.org/
Here is the NCPA station database:
http://ncpa.ampr.org/cgi-bin/database/ncpa.pl
I recommend to start out with finding the "band plan". From that, do you want to
connect to BBSes? Do you want to chat with remote HAMs live? Figure out what
you want to do, change your radio's frequency to the right type of traffic and
listen for a while to see what activity is around.
I've put together some packet maps for California and parts of Nevada here:
http://www.trinityos.com/HAM/index-ham.html#packetmap
There are also various packet nets out there. In Norcal, there is one Sunday
night at 8pm:
http://varmintal.com/ahamp.htm
I also have a very detailed Mheard list that I maintain if you're interested
-------------------------------------------------------------------------------
5. Making Connected Connections
Once you have a working packet setup, you'll want to connect to remote destinations.
This can be done either via CONNECTED or UNCONNECTED sessions. We'll talk about
CONNECTED sessions first.
In a connected session, every step of the communication is tracked and checked. If
there are any errors in the packets, the packet is resent. This is called an ARQ
mode where it retries vs. a mode has extra error correction data in it called
FEC (Forward Error Correction).
Physical TNCs:
--------------
When using a physical TNC like a Kantronics KPC3, you would use the "c"
command to make outgoing connections. For example to connect to the remote
station LPRC3, I would use "c lprc3". If everything is working, I would
get a connection established connection and I would start to see data from
the remote side
Linux
-----
If you have a setup Linux machine, you could use the "axcall" (sometimes
named "call") program to make outgoing connections. Assuming your setup
has everything working and your outgoing interface is named "vhfdrop",
you would make an outgoing connection with "axcall vhfdrop lpc3".
-------------------------------------------------------------------------------
6. Understanding Kantronics KNet and KaNet TNC interfaces
Here on 145.050 in the South Bay Area of California, there are several high level and
low TNCs and other machines you can connect to. The LPRC3, WOODY, KHILL, and KBERR
are all Kantronics TNCS but they can be a bit complicated so let me give you the
secret decoder ring. Most of the TNCs here in Norcal are named after locations.
For example there is BERRY, KBERR, and K6JAC-4 which all THREE names are the *same*
TNC. Why? Specific functions:
K6JAC-4 : this is the specific amateur radio trustee's callsign and SSID. If
you connect to this "K6JAC-4", you will connect to what's called the
Kantronics K-Net node. This is the full featured Kantronics node where
you can connect to the internal Personal BBS (leave simple messages
for the sysop or other callsigns), make outgoing connections (plain
AX.25 and Netrom connections), see remote Netrom routes to other
nodes, etc. Here is what a K-Net TNC prompts look like:
--
BERRY:K6JAC-4} TYPE 'HELP' OR ? FOLLOWED BY COMMAND FOR MORE INFORMATION
BYE BBS CONNECT CQ HELP INFO LINKS MHEARD
NODES PORTS ROUTES STATS USERS SYSOP
--
BERRY : This is an alias for the same above "K6JAC-4" K-Net node just to make it
easier to remember. The chosen name infers that it's up on Mount Berryesa
next to Clear Lake, CA. It's your pick on which name you choose to connect
to it.
KBERR : This is an alias for the Ka-Net node side of the Kantronics TNC (notice the "a"
in there). This is a very simple interface to also make simple AX.25 outbound
connections and list the heard stations. This is also the side of the TNC that
is the UNPROTO digipeater that can be used for unconnected messages, QSOs, and
what we use for the UNPROTO net here on Sunday nights at 8pm. Here is an example
of those Ka-Net TNC prompts:
--
###CONNECTED TO WILD NODE KBERR(K6JAC-6) CHANNEL A
KBERR is the KaNode in the BERRY TNC
ENTER COMMAND: B,C,J,N, or Help ?
--
K6JAC-6 : (a bit of an anomaly here) - this "-6" SSID is configured on the Kantronics TNC
to send data to the RS232 serial port for interactive chatting. The usual
standard here in Norcal is to set this up on the -1 SSID but it's not like that
on this specific TNC for some reason.
As for BBSes, yes, there are BBSes still around. The NCPA or Northern California Packet
Association is our group to coordinate these things and they also have a very nice database
you can check out. Anyway, there are generally two types of BBSes out there these days:
- Classic general purpose BBSes - http://ncpa.n0ary.org/bbsindex.html
- EmComm centric BBSes (here is that database I mentioned)
http://ncpa.ampr.org/cgi-bin/database/ncpa.pl?records_per_page=25&columns_to_view=category&columns_to_view=nodecall&columns_to_view=nodealias&columns_to_view=frequency&columns_to_view=digicall&columns_to_view=digialias&columns_to_view=city&simple_search_string=&sort_field1=category&sort_field2=city&first_record_to_display=25&session_id=d125b05b0a3cb3699961d1abe43019f6&
Many of these EmComm BBSes do support full world-wide BBS forwarding, Internet-based SMTP
email, classic BBS bulletins (called floods), etc. There are all kinds of different BBS
software running out there (JNOS, ARY, FBB, BPQ, etc) so you'll have to figure out which
ones you like!
-------------------------------------------------------------------------------
7. Making UnConnected Connections (UnProto)
Instead of making CONNECTED sessions to remote TNCs, you can send out packets
that are UNCONNECTED. These packets won't get any ARQ / packet retry treatment
but it's a great way to go long distances. You also might be familiar with this
method as this is what APRS uses to sent it's packets!
Here on the 145.050 frequency, you can see the digipeater path people use. They
are almost always prefixed with a "K":
KI6ZHD to DAVID via KLPRC3 KBERR KRDG KCORN KVOLC KBETH TAH0E
It's not a requirement that the "K" be present as it's just a NorCal naming convention
and some NorCal owners have chosen to not follow the standard we put out there. An
example of a non-standard KaNet TNC setup is "Tah0e" or "WOODY"
-------------------------------------------------------------------------------
8. Next Steps:
This document is intended to be a very lightweight intro to packet. To
learn more, I'd recommend to read:
Some of the other recommends intro docs mentioned at:
http://www.trinityos.com/HAM/CentosDigitalModes/hampacketizing-centos.html#5.pkttutor
For a more complete but complex document, read the packet sections
found in:
http://www.trinityos.com/HAM/CentosDigitalModes/hampacketizing-centos.html
-------------------------------------------------------------------------------
9. FAQ:
a. AX.25 vs. Netrom connections
With the software I'm using (AGW Packet Engine and AGWTERM), it seams you can
connect to a call sign via a route. I assume the route includes suggested nodes
like WOODY, KHILL, KBERR. So I'm making an AX.25 connection to the call sign
with the suggested route - right. From there I'm essentially telnetting with
the other call?
Well, it's a little more complicated than that. If your using AGWPE, you're
making basic AX.25 connection to say KBERR (simple Ka-Net node). If you then
made a connection from KBERR to say LPRC3 (a K-Net node), that would also be
a plain AX.25 connection. On KBERR, the "mheard" list would only show remote
paths... *not* Netrom routes. More on that in a bit. Now, let's change it up
a bit.
Let's say you connected from your home station to BERRY (notice the missing K -
this is the full K-Net node) and then made a connection to LPRC3. Since BERRY
is the full K-Net node, it will try to make a Netrom connection to LPRC3 and
not an plain AX.25 connection. If you run the command "nodes", you'll see all
of the *routes* to not only heard remote TNC but remote networks many hops
away. This is what netrom is for.. to let you connect to distant machines
without having to know each hop along the way. Make sense?
b. When I connect to WOODY I seem to be disconnected immediately but a connection
(AX.25) remains up. Know what's going on?
WOODY's signal is very poor these days and I think once you make a connection
request (a very SHORT packet). Then WOODY tries to send you a longer response,
your path is so weak that it keeps retrying and retrying and finally it just
gives up. You need to see if you have better connectivity to other nodes in
your area.
c. What call sign should I connect to for the UNPROTO net?
UNPROTO or UI packets are connectionless.. just like APRS. I'm less sure on
how to send unproto packets with AGWPE in Windows (I'm a Linux guy) . According
to http://www.soundcardpacket.org/4probtx.htm , they say AGW-Term can send UI,
UNCONNECTED or "ASK QRA" packets. I do know that the satellite centric UISS
program can send them well too.
The main Sunday night unproto net web URL is here but is very centric to KPC3
TNCs. I'm happy to help fill in the blanks - http://varmintal.com/ahamp.htm
-------------------------------------------------------------------------------
10. Advanced packet - not using AFSK for the mode; use Fldigi
As mentioned in the 300BAUD HF packet section, this was one of the first
packet modes but it doesn't work very well. The crux of the issue is that
the AFSK mode and the lack of forward error correction hurts it. Modern
modes to the rescue! Programs like Fldigi have long offered many different
HF digital modes that supported different speeds, FEC, ARQ, etc. but they
were only available to Fldigi itself. In recent times, Fldigi now supports
the KISS protocol so just like connecting to a classic hardware packet TNC,
you can now use a software connection to connect the packet AX.25 system
to any mode supported by Fldigi!
I have detailed this in my HamPacket documentation:
http://www.trinityos.com/HAM/CentosDigitalModes/hampacketizing-centos.html#16b.hf-ax25
-------------------------------------------------------------------------------
20. Errata
12/10/16 - Added a note on how to make outgoing Connected AX.25 sessions
- Added URLs for additional reading
- Fixed some misnumber chapters
10/26/15 - Added recommended USB and Rpi images
- Added Next Steps section
- Added Mac options
10/24/15 - First revision
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