1.   Operates and performs upkeep of all types of radio transmitting and receiving equipment and teletypewriter equipment. (1959 Bluejackets' Manual).

2.   Operates and maintains all radio sending, receiving and direction finding equipment. Sends and receives morse code. Enciphers and deciphers messages. Maintains radio batteries. (http://www.naval-reference.net/index.html)

3.    Originally part of the ARTIFICER Branch, later part of Group I.

What They Did:

The Navy Radioman "trade" dates back to about 1914-1918, with the advent of the Marconi wireless transmitter/receiver The Radiomen rating was created in 1921. Radiomen of the US Navy operated and maintained the navy's voice and tone-modulated radio equipment. In addition, Radiomen were responsible for handling incoming and outgoing classified message traffic and for antenna maintenance at both ship and shore stations. The Radioman's work also included the burning of classified messages.

Radioman: Sends and receives encrypted (codes and ciphers) and plain-language messages by radio. Receives messages in Morse code through earphones and records them by typewriter. Transmits with a telegraph key or microphone. May be required to make simple emergency repairs to receivers and transmitters. Must be familiar with the parts of Naval messages, including abbreviations and shortcuts (prosines, etc.); keeps a radio log. Stands watch in radio "shack". (Navy Interviewer's Guide, NAVPERS 16701 Dec 43.)

Radio Technician: Maintains and repairs radios, radar and sonar equipment. Must understand circuit diagrams, principles of various types of vacuum tubes, direct and alternating current, wave theory, etc. (Considerable theoretical knowledge is required) (Navy Interviewer's Guide, NAVPERS 16701 Dec 43.)

Note: In Nov 1999 RM's merged with the Data Processing Technician (DP) rating to form the Information Systems Technician (IT) rating.

Radioman  (RM, RMN)

Qualifications:  (From US Navy Interviewer's Classification Guide, NAVPERS 16701 December 1943)

•  MINIMUM TEST SCORES: GCT 50; SPELL 50; CLERICAL 50; RADIO* 55 (* designates test is of primary importance for this rating).
•  PHYSICAL: Hearing in each ear must be 15/15 by whispered voice. Ears free from disease. Manual dexterity.
•  PERSONAL: No older than 28, unless experienced in code reception.
•  MISCELLANEOUS: Hobby as "Ham Operator," if code work included. Knowledge of typing desirable. H.S. experience desirable

Equipment Used: Radio telegraph, radio telephone, direction finder, typewriter. Radio repair tools, electrician's tools, testing meters.

Types of Billets: All ships; radio stations ashore.

Training: 19 weeks. Practice in sending and receiving Morse code, typing, and hand printing. Naval radio operating procedures. Practical instruction in use of radio instruments and radio-type equipment.

Radio Technician  (RMT)

•  MINIMUM TEST SCORES: Must pass Radio Technician Test; GCT 60; ARI 55; MK ELEC 55.
•  PERSONAL: Manual dexterity. Interest in studying. Age 17 - 40.
•  MISCELLANEOUS: High school training desirable, preferably including algebra, trigonometry, physics, elementary electricity.
   Hobby as "Ham Operator" helpful. Mechanical hobbies dealing with small parts, such as model construction, helpful.

Equipment Used: Long wave, intermediate wave, short wave, and ultra-high-frequency receivers, transmitters, direction finders, underwater sound, Radar, aircraft homing apparatus, control systems, loudspeakers, amplifiers, interior communications systems, echo-ranging equipment, telegraph outfits, storage batteries, motor generator sets, transmission lines. Electrical bench tools, electric meters and testing apparatus, hand tools.

Types of Billets: All but the smallest ships. Shore bases.

Training: Pre-radio: 4 weeks. Course includes elementary mathematics, electricity and radio theory, and radio laboratory. Those who complete this course successfully go on to 12 weeks primary course, including electricity, alternating current, mathematics, mechanics, practical and theoretical study of radios. Those who successfully complete the primary course may qualify for a 24 week advanced course in radio maintenance, including radar and sound equipment.

More info from Wikipedia:

The Radiomen of the US Navy operated the navy's ELF, VLF, LF, HF, UHF, and SHF systems, particularly the tone-modulated radioteletype (RATT) equipment and associated peripheral equipment, such as various types of Teletype Corporation teletypes and teleprinters. Radiomen were also responsible for the prompt delivery of special handling code FLASH, CRITIC, LIMDIS, PERSONAL FOR, various classified message traffic, and other specifically designated messages to their commanding officers shipboard and the associated chain of command.
Radiomen maintained specific job designations, including the operation of satellite and Demand Assigned Multiple Access (DAMA) ship-to-shore shore multiplex systems, the Common-User Digital Information Exchange Subsystem (CUDIXS), the submarine-designated version of CUDIXS, called SSIXS (Sub-Surface Information Exchange Subsystem), and the Naval Modular Automated Communications System (NAVMACS), which was the principle ship-to-shore satellite system.

Radiomen were also responsible for antenna maintenance at both ship and shore based stations. This task was considered most favored because it led to the Radiomen being able to work outdoors and also working aloft on the ship's mast or from the side of the ship. Although the maintenance of antennas was often considered arduous and dirty work, the task of antenna maintenance was generally enjoyed by those Radiomen that carried out these duties.

One of the more arduous tasks that Radiomen underwent included the burning of classified messages. This job meant having to haul down large quantities of classified waste to the ship's incinerator and making sure that it was properly burned and then the ashes mixed with water into a slurry, which was then dumped over the side. This was particularly adhered to, since classified material, if not burned properly, could be read and/or deciphered by operators from those not designated with a need-to-know classification or basis.

Positions held:

Broadcast Operator, Task Group Orestes (TGO) Operator, Message Center, Main-Communications (MAINCOMM) Supervisor, Facilities Control (FACCON) Supervisor, Inbound/Outbound Traffic Checker, Repro/Distro Operator, CRYPTO Operator, Teletype (TTY) Repairman, Inrouter,  Outrouter.

Interesting tidbits

•  Radiomen were traditionally nicknamed "Sparky" or "Sparks," stemming from their early use of spark-gap transmitters.

•  The rating insignia was a set of four lightning bolts joined at the tip.

•  Radio Central was generally known on the ship as the place to go for "Rumor Control" because the Radiomen knew what was going to happen in advance of certain events, particularly sports scores stateside. Often, Radiomen would hold back baseball or football scores for certain "return favors" such as clean, pressed uniforms from the ships laundry.