Introduction to NTS for ARES

This is a written version of a presentation given at the August 2, 2014 Orange section ARES seminar by Dave Bilitch, KI6BHB. Many thanks to Kate Hutton, K6HTN, for providing power point materials from her NTS introductory presentation from which the attached slides borrowed heavily.

The National Traffic System (NTS) is a system of amateur radio nets, procedures and a message format for relay of formal record traffic. The system is designed to provide a predictable routing of traffic, and to promote accuracy and efficiency of message transmission during relay. This presentation outlines

  • how the NTS works
  • how to interface with the NTS
  • suggestions on how ARES groups might use the NTS for training and operational purposes

How the NTS works

The NTS supports three traffic paths which function in parallel:

  • Manual nets - phone/CW/etc.
  • NTSD - BBS like system with automated forwarding
  • Radio Email

Manual Nets


The first path consists of traditional traffic nets (often referred to as manual nets). These are generally phone or CW nets, though its also possible to run manual nets using keyboard digital modes like RTTY and PSK31. The manual nets are structured as a hierarchy with the Trans-Continental Corps (TCC) at the top and section and local nets at the bottom. As one goes up the hierarchy of nets, the nets cover larger geographical areas, with the TCC moving transcontinental traffic between areas of the country.

North America is divided into three Areas (Eastern, Central and Pacific), each Area is divided into numbered Regions, and each Region is composed of multiple ARRL Sections. Each of the areas, regions and sections have corresponding nets, though some neighboring sections within a region may participate in a combined net. Local nets may be organized within geographically large sections.

These NTS nets operate in cycles in a very specific timing sequence. The net times for the evening cycle are

  • 7:00pm - Section net
  • 7:45pm - Region net
  • 8:30pm - Area net
  • 9:30pm - Region net
  • 10:00pm - Section net

The early section and region nets move outbound traffic up the NTS hierarchy, while the late nets bring inbound traffic down the hierarchy. Nets in each NTS area run the cycle at these local times. The effect is for each cycle to ripple across the continent from east to west. Traffic moving from east to west can be at a delivering station in one cycle. West to east traffic must wait a cycle.

NTS defines the following four cycles:

  • Cycle I: 10am - 1pm
  • Cycle II: 1pm - 4pm
  • Cycle III: 4pm - 7pm
  • Cycle IV: 7pm - 10pm

Note that the time for the ending section net of one cycle is the same is the starting section net of the next cycle. So, in fact, these are one and the same net session.

At the present time, only Cycles II and IV are running. The other cycles could be put into service should the need arise. Also, in theory, the manual NTS nets could be activated to run on a continuous rather than a cyclic basis.


Traffic is moved from one net to another via liaison stations. A liaison accepts traffic destined for some later net, and then checks in to the later net to transmit the traffic to the next liaison station. So, for example, a station in Michigan lists a message destined for Los Angeles on the section net. The NCS will direct the station to transmit the traffic to the Eighth Region liaison station. At the region net, the liaison station lists this traffic and is instructed to pass it to the Eastern Area liaison station. This pattern is repeated at the area net and down through the Pacific Area hierarchy where it will be placed in the hands of a local station near the addressee for delivery.

The TCC liaison stations do not run a net to exchange traffic between areas. Instead these stations arrange skeds to move traffic to the appropriate liaison in the destination area.


The second path is the "classic" NTS digital system, NTSD. This is a BBS like system, also referred to as a Mail Box Operation or MBO. Once in the NTSD system, messages are routed automatically using geographical information (usually zip codes) to route traffic to a destination MBO. The MBOs run 24/7, so there is minimal traffic delay.

NTSD uses the same routing structure as the manual nets. Each area and region has an MBO hub, and a section could run its own section hub if desired. There are no liaisions between the hubs as they forward traffic directly over RF, section hubs with region hubs and region hubs with area hubs. There is no TCC in NTSD; area hubs communicate directly with each other.

Messages wait at the destination hub (region or section) for a Digital Relay Station (DRS) to pick up the messages for distribution on a section or local (manual) traffic net. DRS are liaisons which move traffic between the NTSD and manual nets.

Radio Email (Winlink 2000)


The radio email path of the NTS has a completely different structure based on the Winlink 2000 radio email system. WL2K maintains multiple Common Message Servers (CMS) which store email messages in the system and relay email messages between system users and the Internet. Each CMS has a fully replicated message and user database, so any CMS can service any WL2K user request. There are currently five CMS servers located on three continents.

WL2K clients connect via RF to Radio Message Servers (RMS) which relay to the CMS via the Internet. Hundreds of RMS systems are accessible via HF and VHF/UHF all around the world. Client systems may also connect to the CMS via the Internet directly.

If the Internet goes down at the client location, communication with the CMS can be maintain through an RMS outside the service outage. If the Internet is out at one RMS location, other RMS stations outside the service outage area may be used. An RMS station can also be configured to store messages locally should its Internet connection go down, allowing local clients to continue to exchange traffic.

Interfacing with the NTS


The manual and NTSD only relay radiogram format messages. So, we will have to talk briefly about radiograms and hopefully demystify the topic.

The radiogram format consists of a Preamble, Addressee, Message Text and a Signature. With the exception of the Preamble, these map nicely to the To, Message Text and From elements of the ICS-213 message format. While the term Signature conjures only a name and perhaps a title, radiogram signatures may include full contact details including mailing address, telephone, email address, etc. To addressing on local ARES net ICS-213 messaging may need to be expanded, as it should include address and telephone information if available to enable routing and delivery on the NTS.

The Preamble or something like it is necessary once relay of messages is introduced. Direct transmission of formal messages from originating station to destination station allows the opportunity

  • to clarify any ambiguity
  • to log message sent/received time and originating and destination stations/sites
  • to receive the message without delay
  • to avoid the telephone effect

In a relay situation, the originating and destination stations do not have these advantages. The Preamble fields and their uses:

  • Number - uniquely identifies a message - used for reference in replies, requests for clarification or messages regarding relay status, suppresses duplicates
  • Precedence - importance of message - more important relayed first, reduces delays
  • Station of Origin - records station sending the message
  • Check - count of "words" in the text - helps detect errors during relay
  • Place of Origin - identifies the site where the message came from
  • Time and Date - records when the message originated from the site

Radiograms are designed to be mode agnostic. As a result, characters in radiograms are limited to upper case letters and, with the exception of the slash, no punctuation. If a punctuation mark is required, say for a part number, the punctuation must be spelled out as a word, e.g. "part 123-4567-00" would be "PART 123 DASH 4567 DASH 00".

In summary, when converting ICS-213 to radiogram:

  • Copy To to Addressee adding mail address, phone, email as needed
  • Copy From to Signature adding return address,etc if needed
  • Reformat Message Text to eliminate punctuation, make message brief, be mindful that letter case is not preserved
  • Add a Preamble

Manual Nets

Interfacing with the manual NTS nets is simply a matter of assigning liaison stations to bring and receive traffic on an NTS net. Only basic radios and accessories are required. Some training and practice is helpful which is available on the nets.


To connect to the NTSD, a computer configured with winlink "classic" software, a Pactor TNC, an HF radio system and an old Windows computer are required. The software only runs on older Windows system (Windows 98 and down). Then your region (or section) hub station can be configured to send traffic for your local area when you connect. This is usually the function of a Digital Relay Station to move traffic between NTSD and the section and local manual nets.

Traffic can be sent into the NTSD via radio email addressed to one of the area NTSD hubs. This requires that the radiogram traffic be formatted into a batch file for importing into the NTSD software. The batch file adds digital routing markup to each radiogram. A program, NTSD Parser, is available that will add the markup to a text file of radiograms. Then the file(s) may be sent via radio email to an area hub.

Radio email

The Winlink 2000 system requires a radio, a Pactor, packet or WINMOR (software) TNC and a Windows computer configured with client software. If the WINMOR sound card TNC is used, it is recommended that a stand alone sound card interface be install and used rather than the default Windows sound card. However, the default sound card may be used with suitable Windows audio settings.

The recommended Winlink 2000 client is RMS Express, and is the only client which supports the WINMOR software TNC. Other clients are Airmail and Paclink.

The Winlink 2000 system, while supporting transmission of radiograms in the email text body and as attachments, also allows free form emails with attachments. So ICS-213 format messages may be sent as attachments or in the body of an email message. With the exception of .exe and .zip files, any type of attachment is allowed.

So why use radiograms if email is available? Email can only be relayed through the Winlink 2000 system, and received if the destination has functioning email capability. Email traffic would be difficult to relay to a site in this kind of condition; generally, attachments could not be relayed at all.

Should email traffic be desired, keep in mind the bandwidth limitations of RF paths before sending large attachment files. In general, attachments should be kept as small as possible; use of plain text formats in lieu of word processor files is recommended. RMS HF gateways have time based usage limits.

Transmit times for 4k message in ideal conditions

Packet (1200) direct 2 minutes
Packet (1200) 1 Node 2.5 minutes
Packet (9600) direct 1 minute
Pactor 1 15 minutes
Pactor 2 4 minutes
Pactor 3 30 seconds
Pactor 4 15 seconds
WINMOR 3-10 minutes, depending on the Bandwidth used
Telnet (Internet Access) seconds

Suggestions for ARES groups use of the NTS

  • NTS nets are running 365.25 days a year. Use them as training for directed net operations. Some of NTS voicing procedures may be helpful for ARES message and tactical traffic.
  • If contemplating radio email, have ARES operators spend some time as digital liaison stations. We will route radiograms via radio email to the station who brings them to an NTS net for distribution. Could also route outbound traffic through the ARES station.
  • If contemplating using NTS, discuss your use case with STM and/or net managers. This will help us with activation plans, or get us in the loop to help ARES set up NTSD or radio email.


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