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Digital Operations Guidelines |
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| Written By: Ben Sager, KC4ASF | Release Date: January 3, 1998 | |
| Latest Revision: Sept 12, 2004 |
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Purpose
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Background
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Part One: Operations
Networks
Local Operations
Protocols and Frequencies
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Part Two: Virginia EOC Operations
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Part Three: MARS Operations
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Part Four: Parameters
TNC Parameters
Node Parameters
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Part Five: Glossary
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Part 6: Packet Training
Purpose:
To provide guidelines and uniformity to amateur radio operators using digital communications to assist with communications between the State of Virginia Emergency Operations Center (VA EOC) and affected areas of the state during emergency situations.
Background:
Contrary to the thinking of some amateur radio operators, radio frequency digital communications has not been replaced by the Internet, but is an adjunct to the wire line network. Internet messages and information sharing play a significant role within VA. When the electrical power or telephone lines are down, amateur radio traffic can still get through.
VDEN is dedicated to the use of digital communications that transmit messages during times of disasters and/or other emergencies. Digital communications has the ability of providing messages, without errors, in a written format. During the Franklin area flood in 1999 over 700 messages were relayed using VDEN digital communications! The Virginia Department of Emergency Management has requested that VDEN provide digital communications coverage to all areas of the Commonwealth.
Part One: Operations
NetworksSome of the stations operating on the Virginia HF digital network will be K4VDN, KC4ASF (Fredericksburg), KR4MA (Tidewater) and W4ZA (VA EOC Richmond). KR4MA is operational on 3.620 LSB 24/7. These stations have VHF/UHF ports for local operations and forwarding. The ideal setup would be a HF/VHF digital setup in each District and a dual VHF/UHF setup in each county. Each County in VA should have two ES's (Emergency Station) with digital capabilities.
The primary VHF 1200bps user frequency for the VA EOC and
VDEN is 145.73 MHz. This does not mean that you must setup
on 145.73 MHz. If an area of the state has an operational
packet network on a different frequency, a simple link to the
VDEN network is sufficient to support your mission.
A 441.050 MHz network using 9600bps now links
Richmond and Tidewater. Backbone frequency 446.075 MHz, using
1200bps, is used as a parallel backbone network to support
the 145.73 network from Richmond to Northern VA. Development of
VHF/UHF routes into South and Southwest VA are well under way. As
of this writing, over 90% of the state now has digital coverage.
51.28 MHz may be tested for 9600bps forwarding around the state.
All frequencies have cross-links to each other.
Traffic forwarding should be kept off 145.73 MHz frequency whenever possible. Keyboarding is not an accepted mode during activations on 145.73. Stations are asked to halt forwarding of all bulletins not related to an activation and whenever a drill is going on. The network should be notified with a bulletin to ALL@VANET whenever a drill is to take place.
- It is strongly recommended that each district and county in Virginia have one primary and one secondary Emergency Stations (ES) with digital capabilities.
- These stations should be located wherever local and state officials think they will be most useful.
- They should not be at the same location.
- These stations should be equipped for HF and VHF/UHF digital operations. A full BBS type operation is not necessary. Terminal and host mode programs will work fine.
- Placement of multi-mode TNC's at the state and district levels should be given top priority. Simple VHF/UHF TNC's such as the Kantronics KPC-3 (Version 5.2 and above) can be placed at a central location or locations in each county.
- The local level TNC's should have reverse poll capabilities. This will allow the BBS stations to reverse poll the local TNC for traffic regularly, this will help prevent the congestion normally associated with each TNC trying to get a message through.
- Once the BBS has a message, it should pass it to the VA EOC using whichever method works best.
- If the VA EOC is not reachable directly, the next station in
line should take the message for further forwarding.
"Next station in line" is defined as any station capable of forwarding the message on towards its final destination. The stations and paths that you will use for such forwarding should be determined in advance. Don't waste your time and tie up the system trying to force forward a message through multiple nodes. Get the message to the next station in line and let the system work as it was designed. NEVER use keyboard-keyboard on 145.73 during an activiation or drill. - Simplex operation (without nodes) should be used whenever possible. Not only does it ease network congestion under normal conditions but there is the possibility that a remote node may be down during a real activation. Stations should experiment operating in the simplex mode to find what setup works best for them including using six and ten meters at the local and district levels.
To accomplish our objectives we need to have redundancy and utilize all means of communications at our disposal. The primary frequencies used by VDEN are VHF and UHF. We use HF to not only supplement but provide redundancy to the VHF/UHF. We use internet email as another form of backup.
- VHF/UHF:
- A Packet program using AX.25
protocol with FBB compression is the preferred VHF/UHF mode. JNOS
which uses TCP/IP protocol is also used in
some locations. MSYS is our most widely used AX.25 BBS program. A
MSYS "plug-n-play" setup program is available on the
digital website VDEN.
- HF:
- Pactor is the preferred mode for HF digital operations since its ability to get through interference is well known.
Frequencies and Transmission Speeds
| Net Designation | Frequency MHz | Mode | Speed | Usage |
|---|---|---|---|---|
| VA Emergency Net Echo (VEN-E) | 145.730 FM | Packet | 1200 BPS | User Primary |
| VA Emergency Net Foxtrot (VEN-F) | 446.075 FM | Packet | 1200 BPS | Forwarding & Users |
| VA Emergency Net Golf (VEN-G) | 441.050 FM | Packet | 9600 BPS | Richmond to Tidewater Forwarding |
| VA Emergency Net Hotel (VEN-H) | 51.28 FM | Packet | 9600 BPS | Forwarding |
| VA Emergency Net Delta (VEN-D) | 3.620 LSB | Pactor | 300 BPS | Primary |
| VA Emergency Net Delta (VEN-D) Alternate | 7.105 LSB | Pactor | 300 BPS | Alternate Days |
Part Two: W4ZA SOP (includes NTS format)
See the W4ZA Standard Operating Procedures attachment.
Part Three: MARS Operations
We realize that the MARS systems have many good frequencies as well as many qualified operators trained in message relay and ECOM situations. Cross-links between amateur and MARS digital operations can be used to relay messages to the state EOC using the VDEN system. MARS callsigns should not be used on the message once it has been entered into the amateur network. The message should contain the amateur callsign of the originating station, i.e., KC4ASF/AFA2OS. The station that transfers the message to the amateur network is responsible for changing the MARS callsign in the address to the amateur callsign of the originating station. The standardized message format (NTS) used for ECOM messages should be used. However, NTS is clunky and may be replaced.
Part Four: Parameters
We know that standardized parameters make a tremendous difference in the through put of the network. Therefore, we offer some VHF/UHF parameters for 1200bps AX.25 packet operations. All operators are encouraged to follow these parameters.
TNC Parameters
Frack 4-6
ID E 45 Minutes
Numnodes 2
MaxFrame 2
MAXUSERS 2
Paclen 125
Persist 63ms*
Response 2
Retries 10
Slottime 10ms* (adjust to 30 when used with TCP/IP systems)
TXDelay 35
Unproto VDEN
Users 2
* Check your TNC manual to determine the timing rate used.
Node Parameters
Digipeat On
Frack 4-6
Heard List 25
Link Retries 10
MAXFrame 2
No Activity Timeout 600 seconds
Node Broadcast 60 Minutes
Obsolescence Count Initial Value 5
Obsolescence Count Minimal Value 3
PPersist 63
Minimum Quality for Auto update 63
Radio Channel Quality (HDLC) 192
RS232 Port Quality 255
Response 2
TXDelay 35
Part Five: Glossary
- AX.25 Protocol
- A modem protocol adapted for use in amateur radio digital operations. It is the most widely used mode of digital communications. There are other modes such as TCP and the TOR modes. Back
- BBS
- Bulletin Board System is an electronic bulletin board service maintained by an individual or organization for the primary purpose of exchanging information.Back
- FRAME
- A block of data that not only includes the information for the other station but also the information necessary to get it there. A packet can consist of multiple frames of information.
- GATEWAY
- A gateway is a nodestack or routing software setup that allows multiple frequencies to be in use at the same time. You can come into the gateway on one frequency and go out on another. You can also come into a gateway using one type of protocol and go out using another. TCP/IP (internet) connections are available at some gateway stations.
- HTS
- Hidden Transmitter Syndrome. This is the single biggest problem in packet radio. It is a station that is not heard by one or both stations trying to communicate. The interference causes retries and timeouts.
- IP
- Internet Protocol. The workhorse protocol of the TCP/IP combination.
- KISS
- Keep It Simple Stupid. This is the widely used method of TNC to Terminal control.
- MULTI-MODE
- A TNC that has HF and VHF packet plus the TOR modes which includes Pactor. The Kantronics Kam Plus is an example.Back
- NEIGHBOR NODE
- An adjacent node which can be reached in a single hop. Packet networks consist of many nodes, some of which are neighbors and the rest are distant nodes which depend on intervening nodes to complete the path.
- NET/ROM
- This is a networking software used for nodes.
- NETWORK
- A collective term used to refer to a set of nodes with their neighbors, routes, paths, etc., which make up an interconnected collection of packet radio facilities capable of transporting information between stations. Back
- NODE
- The fundamental hardware building block of packet radio networks. At a minimum, a node will consist of a TNC capable of running some type of routing software such as TheNet and X1J. More complex computer based routers such as the G8BPQ node code and the multi-level communications server methods used by such programs as MSYS, FBB, TCP (NOS) and FlexNet which is gaining popularity.
- NODESTACK
- Is the common name for nodes that employ two or more TNCs, each of which is connected to a radio via its own radio port and to all the other TNCs via the cabling of a multi-drop serial cable.
- NOS
- Network Operating System. This is the basic TCP/IP software package for packet.
- Emergency Station
- An appointed amateur radio station that has complete emergency communications capabilities and participates in drills and exercises.Back
- PACKET
- A mode of digital transmission where data is assembled in groups of data or frames of information. A packet of data consists of two or more frames.Back
- PACTOR
- A digital mode used on HF which has a high reliability of getting through under adverse conditions.Back
- PARAMETERS
- The TNC used in a digital system has various setting which must be programmed by the operator to obtain the best performance for its particular function. These setting are called parameters and are different for each use, e.g. user station, node, etc. Back
- PATH
- A path is a complete circuit between two packet radio stations. A path may cover several routes and nodes to bridge two stations. A path may travel over a number of frequencies and may involve hardwired (cable) connections as well radio (RF) links.
- PMS
- Personal Message System is the term applied to a simple private TNC based messaging (mailbox) system.
- PORT
- All nodes have one or more ports. A port in this discussion is a physical interface between the TNC and a radio such as a cable connection. A typical TNC will have at least one radio port and one cable port usually an RS-232 connection to a computer running some type of communications software.
- PROTOCOL
- A set of rules used for communication. This can include the speed used, the number of bits, the mark and space frequencies. In packet radio, AX.25 is the form of protocol. Back
- ROUTE
- A one hop path between two neighbor nodes and the fundamental element of a path/circuit.
- SSID
- Standardized Station ID's in VA are a -1 for BBS's, i.e., KC4ASF-1 and using no SSID for the keyboard such as KC4ASF. TCPIP operators use -8 as their SSID for the BBS. MSYS netnodes use -3 and Kanodes use -7 SSID's. It is simplest for BBS's and TNC based operations to use the same SSID's. ALL non-forwarding stations should clearly state in the Connect Text that they do not auto-forward.
- TCP
- Transmission Control Protocol.
- TCP/IP
- Transmission Control Protocol/Internet Protocol is protocol used primarily on the Internet, but has also been adapted to some forms of amateur radio digital transmissions. The VA EOC BBS uses MSYS.Back
- TNC
- A Terminal Node Controller is essentially a smart modem designed for packet radio. It operates using Bell 103, 202 and 212 modem standards. It is the device used to interface the radio and terminal. Back
- WORMHOLE
- This is a vague term, it refers to a communications link between two widely separated communications facilities. A wormhole has the ability of making the two distant facilities appear to be connected directly to each other. Such a wormhole exists between the Richmond and the Tidewater area. Wormholes are usually landline based.Back
Part Six - PACKET TRAINING
A Packet Primer prepared by Jim Dodd (KF4LGV) for VDEN (VA Digital Emergency Network) is available at http://ham.eitinc.com/PACKET.html. This article is an excellent source of information for people new to packet. There is also a guide for sending NTS messages on the VDEN home page entitled "NTS Made Simple".Additional references for basic packet are:
TAPR -
Packet Primer - Why Packet Radio?
TAPR -
Introduction to Packet Radio
NorthEast Digital
Association
FlexNet
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