An ARRL radiogram is an instance of formal written message traffic routed by a network of amateur radio operators through traffic nets, called the National Traffic System (NTS).
It is a plaintext message, along with relevant metadata (headers), that is placed into a traffic net by an amateur radio operator. Each radiogram is relayed, possibly through one or more other amateur radio operators, to a radio operator who volunteers to deliver the radiogram content to its destination.
Form overview
Radiogram forms facilitate a standard protocol between amateur radio operators, allowing much faster relay of formal messages. They do this by always having the message headers in a certain order, allowing operators to read and understand the headers without explicit verbal labels. This is especially important in hectic and stressful environments such as during a disaster, when many parties call upon radio operators to quickly transfer messages in and out of the affected areas.
A typical form has a place for the plaintext message, as well as for several headers that are important for routing the message to its proper destination in a timely manner. These fields include the message's priority, the callsign of the station of origin (the amateur radio operator who placed the message onto the message net), the date and time of origin, contact information of the message's recipient, as well as the callsign of the station that delivered the message.
The headers' purpose and order is logical and intuitive enough that many amateur radio operators have memorized it and in extremis can transmit and receive radiograms without referring to the form.
Current ARRL Radiogram
Preamble part
All messages must have a preamble. The preamble of the message contains information about the message necessary to keep track of it as it passes through the amateur system. The parts of the preamble, except for the check as noted later, are not changed by any station relaying or delivering the message. They are permanent parts of the message created by the station of origin and must remain with the message all the way to the delivery point. Preamble information is used to service undeliverable messages and to generate replies to specific handling instructions.
Message number
The message number is selected by the station originating the message and it must be on all messages. It stays with the message all the way to the point of delivery. The delivering station may need to reply to the station of origin and refer to this number. Use number digits only, no letters, leading zeros, or dashes. Numbers are usually begun with 1 at the start of a year or month at the pleasure of the originating station.
Message precedence
Letter(s) used to indicate the precedence of the message, and must be on all messages. See the latest Precedence full definitions from ARRL (From ARRL FSD-3).
Precedences
PRECEDENCES (ARRL FSD-3, 2/94) EMERGENCY (Spelled out on form.): Any message having life and death urgency to any person or group of persons, which is transmitted by Amateur Radio in the absence of regular commercial facilities. This includes official messages of welfare agencies during emergencies requesting supplies, materials or instructions vital to relief of stricken populace in emergency areas. During normal times, it will be very rare. On CW/RTTY, this designation will always be spelled out. When in doubt, do not use it.