Josephine County ARES Packet Info
The Packet Network
In the Southern Oregon/Northern California region covered by SOAPRA, two separate networks are in operation. They are as follows:
Some general conventions for using the network:
Frequencies - Nodes
145.01 is a general use non-protected frequency for experimentation, personal traffic, etc. Any nodes on this frequency are not coordinated by the regional frequency coordinators and are probably there for test purposes.
144.39 is the National APRS frequency. We don't have any APRS digipeaters set up at this time, have been using digipeating through local keyboard network nodes when we have been experimenting with it.
144.910 through 145.090 on 10kc channels is assigned to packet under the Oregon Regional Relay Council (ORRC) bandplan. It is best to use local frequencies 20kc in separation to avoid cross channel interference
What is Packet
The Basic Station
A basic packet radio station consists of a Computer, Terminal Node Controller (TNC) and a Radio.
Noise On The Air
Packet operation is similar to simplex voice radio operation. Listen before you key up on the frequency! If you are transmitting, you can't hear! If someone keys over the top of you, you get a double and nothing intelligible gets out!
To handle multiple people operating on packet, the TNC uses a method called Carrier Detection (CD). It listens to the frequency to make sure it is clear before transmitting. If two stations do transmit at the same time, this is called a collision. The receiving stations cannot detect any data when this happens. The transmitting stations at this point get no acknowledgement and try to retransmit. TNC's have a function called PERSIST/SLOTTIME that helps them to not do this retransmit exactly at the same time again.
Just like voice operations, repeaters are used to extend the range. You can even use a linked repeater system to extend the range further. Unlike most voice repeaters, though; packet repeaters operate in simplex mode. This means that they have to receive the packet, store it and then retransmit it. Packet repeaters have two different names, depending on the type of operation. They are called either digipeaters or nodes.
Who Am I Addressing
For your station to effectively get on the air, you have to give it an address. Just like getting postal mail or internet e-mail, there must be a starting destination and an ending destination, otherwise you are merely heating the air with RF energy. The simple method used in Amateur Packet Radio is to assign your call sign as the address.
Now this is pretty good if you just want to communicate between two individual stations, but what if you want to also have a mailbox and a node on the same frequency at one of those stations, for example KC7WIS? Stations attempting to connect would have a hard time determining which device was really KC7WIS now, and KC7WIS would have a hard time determining which personality to display! To get around this problem, a number referred to as an SSID is appended to the address call sign for the subsequent identities.
There are 16 SSID's available. In our earlier example this would give us KC7WIS-0 through KC7WIS-15. The -0 SSID is equivalent to the address call sign. Using the SSID now, we can assign the station call as KC7WIS, the mailbox (PBBS) as KC7WIS-4 and that KA-Node as KC7WIS-8. Now this TNC can take on several functions at once, serving as a keyboard device, mailbox and node all under one call sign.
Let's Get Connected
Packet Radio can operate in an unconnected mode sending out what are called UI frames or Unproto Packets. To do this, choose a clear frequency, turn your TNC monitoring on, put your TNC in convere mode, type in a message and send it. The other station can do just the same, and you can keyboard back and forth. This is the simplest method of communications with packet.
There are advantages to using the unconnected mode. In weak signal work, you can turn a function called passall on and it will display all received packets whether they pass the error correction or not. This of course puts the interpretation as to what was received on your shoulders, but eliminates failure to receive a packet because it was partially corrupted. Also in modes such as APRS, hit or miss methods work quite well since the data will be repeated at intervals.
The main disadvantage comes about when you try to share a frequency between more than two stations. You now find out that Monitor displays all packets transmitted on the frequency. If you are running a roundtable chat, that is fine as you pass the speaker's staff to the next person in sequence, but what if you have four stations that want to hold two individual conversations?
In technical terms connection or linking is the action of forming a virtual ciruit using the network resources available. Doggonit, speak English! Ok, connecting is one TNC informing another TNC that it wants to hold a private conversation without all those others butting in and spewing unwanted information all over your screen. Now, two or more pairs of stations can send data or messages independent of the other pairs.
The basic connect takes place from station to station. What happens now if you are trying to connect to a station that is just out of range? You ask an intermediate station to repeat your message to the end station.
Two different types of stations are used for repeating Packet transmissions:
Digipeating: This is the simplest form of repeating. All TNC's can act as digipeaters. You can connect to the end station via a chain of up to eight intermediate stations. It has the advantage of being slightly faster in transmitting the messages along the chain on a clear frequency; however, only the end stations check the packet for errors. If an intermediate station in the chain receives a corrupted packet, it just passes it on to the end station which then has to send a request for retransmission all the way back to the originating station. A digipeater circuit can degrade and fail very quickly with excessive traffic or interference.
Node Network: Nodes are a special form of packet station. Some TNC's have one built in, most Nodes are TNC's with special software for dedication to this use. You can connect to the end station through about sixteen Nodes. As a packet travels through a network, each Node checks the packet for errors and asks the previous station to resend it upon detecting errors. This allows for more efficient operation as the system discards garbaged packets immediately instead of passing them all along the network to the end station to be tested for corruption.
Another advantage to Node networks is that they are designed to learn about each other's ability to connect. This means that you can connect to a local Node, check its node list to see if a node exists near the end station, connect to that node and then connect to the end station. No knowledge is needed about all the intermediate stations call signs, frequencies, etc. The connect command propagates through the network until it establishes the connection with the desired station.
Since we are using Kantronics TNC's, we need to also discuss KA-Nodes. Most Kantronics TNC's have KA-Node capability. The KA-Node is a special limited node that allows you the advantages of a node's station-to-station error correction while not littering the air with all the node routing traffic or inserting itself into the network's routing tables which can cause real havoc when you shut it off after a packet operating session. To use a KA-Node, you must know it exists. To use a basic network of KA-Nodes, you must know the call signs and individually connect to each one.
Packet Radio allows you to take computer input, assemble it into addressed packets with error detection and transmit these packets over the air to another station. For more distant transmissions, the packets can be digipeated or sent through a node network.
Basic Kantronics TNC Commands
Before you get started, you must understand that a TNC has two separate operating modes:
Command Mode: This is signified by the cmd: prompt. All TNC commands for setup, connection, disconnection, etc. are entered here. You can reach command mode at any time by holding down your Control key and then typing C (CTRL-C).
Converse Mode: Most TNC's are set up to immediately put you in this mode upon connection to another station. In Converse mode, anything typed and then followed by an enter is transmitted over the air. You can get to Converse mode from the cmd: prompt by typing K and then enter.
Your Kantronics TNC has a very nice feature. Type HELP at the cmd: prompt, press enter and it lists all the TNC commands available. Type HELP followed by the command, then press enter and it tells you what that command does, usually with a short example of the command and parameters that need to be entered.
The following commands set the address call sign the packet station operates under. Check these when the station operator changes:
The Least you need to know to get started:
The following commands set monitoring functions so you can observe frequency activity:
Basic PBBS Commands
Basic Node Commands
Basic Full Service BBS Commands