Radio



In military use, radio systems are used to pass on orders and communications between field, command, and support personnel, with radio transceivers used extensively in intelligence gathering operations. The technology has continued to develop for many decades, resulting in such communication systems as the Codec.

Cold War
During the Cold War, the Soviets as well as the FOX unit utilized radios to communicate with their higher ups during missions. The radios consisted of a turn-knob device on the right side of the soldier/operative's utility harness, used to allow them to receive the call when it rings or if they want to contact support for any reason, as well as a wired microphone that is situated near the ear. However, at the time, the radio being used by each member of a squad was not a fully realized concept, and thus various squads in military factions, such as GRU during the 1960s, often needed a radioman in close proximity to be able to report to HQ during patrols.

By the 1970s, a radio system was developed to include a circuit that reverses the audio phase as a means to conceal any operatives involved. Overall, it resembled a standard transceiver. The KGB agent Vladimir Aleksandrovich Zadornov, while using the identity of Professor of Peace Ramon Galvez Mena, had a radio in his office in Ciudad Colon, which he allowed Paz Ortega Andrade, one of his students, to use to maintain contact with Big Boss and the MSF during the time of the Peace Walker Incident, with MSF's subcommander Kazuhira Miller having modified the radio to allow contact with her.

FOXHOUND radio systems
During the 1990s, U.S. Special Forces Unit FOXHOUND used transceivers that allowed satellite communication from anywhere in the world. By utilizing burst-conversion signals via computers, decoding of transmissions by the enemy was prevented, even if an operative was captured. FOXHOUND members were nonetheless required to destroy the radio upon capture to keep America’s involvement a secret.

In the 2000s, FOXHOUND adopted the Codec system. Invented by Mei Ling, it incorporates anti-wiring coding, digital real-time burst communication. A normal communication over ten seconds is instantly codified, compressed, and transmitted in a burst one microsecond in length. It is received in real-time, unscrambled, and decoded. It is incomparably more innovative than the conventional anti-wiring frequency scrambler. The 24-hour system that is unaffected by weather is made possible by integrating information from high-altitude reconnaissance satellites and low-altitude reconnaissance planes. Despite this, substantial restrictions such as environmental harmonic resonance, enemy discovery and very low structures over an operative have caused significant interference in past testing.

The Codec functions by directly manipulating the small bones in the ears, such as the stapes, so it appears as if a user is talking to himself or herself. Furthermore, the Codec can process and send photos to people within its network from a digital camera,  and had some capability of video communication. During the Big Shell Incident, the Codec was primarily nanomachine based, and people wired with nanomachines will also engage in nanotech-based speech while outwardly appearing silent. However, the nanomachine based Codec model is nonetheless compatible with the older Codec models as well as standard military radios. The Codec could also upload websites, as demonstrated by Snake uploading various sites to Raiden that contained pictures of the Metal Gear RAY prototype that Snake had previously uploaded during the Tanker Incident. By the time of Liquid Ocelot’s Insurrection against the Patriots in 2014, the Codec was implemented into Metal Gear Mk. II via videoscreen. The Codec remained in use by 2018, with it now giving visual displays of mission support to operatives via a holoprojection screen. Because of Raiden's reconstruction surgery after the doomed mission in Africa supplying him with an optical implant in his right eye, he can also effectively "see" his mission control talking with him if he otherwise can't use the holographic display. Similarly, the optical implant acted as a two-way channel, allowing for mission control to see from the operative's point of view. The Codec also can be adjusted to broad direct-spread sequence spectrum within the blue-1 frequency hopping pattern, with its systems also keeping the interference below process gain, and could communicate between Maverick HQ's data storage and the operative's tactical data line, with the overall increase in latency being below five percent, which is especially useful when undertaking missions not officially sanctioned by Maverick, as it ensures that enemy operatives are unaware that Maverick is even transmitting Codec frequencies, much less listening in. The contacts also contains basic information on their identities, including their age (if applicable), their gender, their height, their country of origin, and their allegiance (if applicable). The Codec, similar to the 2009 incarnation, can also monitor frequencies from other radio models. Besides Maverick, the cyborg members of Desperado was also utilized the Codec.

Other usage
The Gurlukovich Mercenaries utilized two types of radio systems: one system, used primarily by grunts, was similar to the system utilized during the Cold War regarding a radio knob on the right shoulder of a harness. The other system was a standard radio system dating back from late World War II, early Cold War that resembled a huge cell phone, these were primarily utilized by the top leaders of the Gurlukovich Mercenaries; Olga and Sergei Gurlukovich. Liquid Ocelot utilized the latter radio system during his test in the Middle East. The Dead Cell members also wore radio implants within their ears to relay orders to each other by the Big Shell Incident. In addition, Meryl Silverburgh's team Rat Patrol utilized a SINCGARS radio system to contact Snake via the Codec when she discovered that, contrary to Snake's earlier claims, he was actually in the Middle East to assassinate Liquid Ocelot, not deal with threat assessment. During the events of Desperado's occupation of Abkhazia, Mistral and Dolzaev utilized miniature radios to communicate with each other. Raiden also briefly utilized Mistral's radio shortly after she died when demanding for Dolzaev to surrender, nearing the end of his mission to quell the occupation.

Vacuum radio transmitter
A briefcase-sized transmitter that comes with a wired microphone, and utilizes various dials. During Operation Snake Eater in 1964, EVA used this to contact the Chinese government until it was destroyed by Colonel Volgin with his electricity. She later used a second one after she and Naked Snake arrived in Alaska, and spent the night in a lodge, although she later destroyed it by throwing it into a fire.

Fixed-set dial system
A fixed radio system was utilized during 1964 within Bolshaya Past's supply depot in Tselinoyarsk, and during the San Hieronymo Takeover on the San Hieronymo Peninsula's communications base and in the radio tower at the ravine. It is through this system that Naked Snake made contact with Para-Medic and Sigint in the latter event.

Headset
A type of listening device: It utilizes two pads connected to a bended strip to accommodate the cranium that acts as the audio receiver of radio transmissions. They sometimes come with a miniature microphone.

During the Virtuous Mission and Operation Snake Eater, Para-Medic and Major Zero utilized headsets. Likewise, The End was seen wearing headsets. During the San Hieronymo Takeover, various members of FOX utilized yellow and black headsets. Roy Campbell also wore headsets during the same incident. Similarly, during the Peace Walker Incident, the Peace Sentinel soldiers utilized headsets. The MSF subcommander Kazuhira Miller also wore headsets while he was piloting the Huey. The Intel Team member Hideo also wore headsets.

During the 1990s, the FOXHOUND unit utilized lightweight flexible headsets with a high-performance microphone that can amplify sounds in the ear without the need of a loudspeaker by directly stimulating the small ear bones, although FOXHOUND members were required to destroy the headset upon capture to keep America's involvement a secret. In addition, the mission support group also utilized headsets.

During the Big Shell Incident, Iroquois Pliskin utilized a headset normally used by SEAL commanding officers when infiltrating the Big Shell, which also clued in that he was not actually a SEAL operative.

During Liquid Ocelot's Insurrection against the Patriots in 2014, Pieuvre Armement and Praying Mantis utilized headsets, the former PMC utilizing Com-Tac Ballistic Headset brand and MBITR transceiver radios, and the latter utilizing the Peltor COMM-TAC II Headset brand. Otacon also utilized headsets when piloting a helicopter.

During 2018, Sunny wore some green headsets around her neck. Doktor also wore headets while piloting a helicopter in semi-auto mode.

Cochlear implant
During the 2000s, FOXHOUND operatives as well as Solid Snake utilized a cochlear implant to better disguise the Codec's receiver from the enemy.

Nanomachines
Prior to infitrating Shadow Moses Island in 2005, Solid Snake was given a shot by Naomi Hunter during his mission briefing, which included a nanomachine base that would recharge the Codec's batteries.

During the late 2000s, a nanomachine-based Codec was utilized by various soldiers and operatives. In order to successfully prevent outside people from successfully listening in to the call, the operative speaks in a nanomachine-based language while externally appearing to be silent. After meeting with Raiden on board the Big Shell, Emma Emmerich realized that he was not working for the Sons of Liberty terrorists, due to his possession of Codec-enabling nanomachines.

Micro-radio transmitter


During 2018, these radio systems were utilized by the Desperado forces stationed at Abkhazia and by their client, the European extremist Andrey Dolzaev. After Mistral was killed, she used this radio to contact Dolzaev in her dying breaths. Raiden later used this same radio to demand for Dolzaev's surrender, although Dolzaev refused in a reply that Raiden deduced from his words meant he was going to commit suicide by blowing something up.

Civilian usage
Radios also can be used by civilians as well as military. Although most are used as a communication device similar to military radios, others have completely different purposes, such as recreational entertainment.

In 1964, the lodge Naked Snake and EVA stayed at shortly before the latter was summoned to Langley for a special ceremony regarding the success of Operation Snake Eater, had a radio that played music.

Nearly ten years later, during the Peace Walker Incident, the Peace Sentinel AI researcher, Dr. Strangelove, utilized a radio that played Sing by The Carpenters, immediately prior to commencing torture on Naked Snake/Big Boss, the commander of the Militaires Sans Frontières, after his capture at the Mine Base.

During the Liberian Civil War, Solidus' main office at the Army of the Devil's main encampment contained a radio, which he used to play music for Raiden when lecturing him on the "nobility" of bladed weapons.

Behind the scenes
The radio has remained a staple of the Metal Gear series since its inception. It allows the player character to contact their mission support team who offer advice on how to proceed within the game, along with additional information on the game’s setting and environment. Optional conversations are also common in the series, and can be initiated by the player at certain points during the game’s progress.

Radio Mode
The radio can often be interacted with via an interface separate from the main game screen, variously referred to as the Transceiver Mode (Metal Gear, Metal Gear 2: Solid Snake), the Codec Mode (Metal Gear Solid, Metal Gear Solid 2: Sons of Liberty), the Codec Screen (MGS, MGS2, Metal Gear Solid 4: Guns of the Patriots), the Radio Mode (Metal Gear Solid 3: Snake Eater, MG, MG2 ) or the Radio Screen (MGS3, Metal Gear Solid: Portable Ops). The screen comprises a digital readout, displaying the frequency to which the radio is set, portraits of either the player character (MG), the supporting character (MGS4, Metal Gear Solid: Peace Walker, Metal Gear Rising: Revengeance ), or both (MG2–MPO), and a window in the lower half of the screen, displaying the characters' dialogue in text. The portraits consist of either static or animated artwork, or in later games, fully 3D polygonal models.

During the game, support personnel will contact the player character, in which case the radio will beep and the word "CALL" will flash onscreen. These calls are either mandatory, with the transmission automatically accepted, or optional, allowing the player to ignore it. In order to contact another character, the player must input the relevant contact frequency and use the "SEND" function. In older games in the series, the player must make note of certain frequencies, which are only provided under specific circumstances, and are sometimes only given once. In later games, the Memory Window was introduced, consisting of a drop down menu that would display any frequencies that the player has made or received contact with. This was later retroactively incorporated into the re-released versions of the older games.

Early games
In Metal Gear (MG), the radio provides basic information on various items or boss characters, either by request or by call reception, and is dependent on the player's location. In the non-canon Snake's Revenge, the contact's appearance is displayed in the Transceiver Mode for the first time in the franchise. Metal Gear 2 (MG2) expanded on the radio's use, allowing greater detail to be relayed to the player regarding boss characters, locations, and even the player's currently equipped weapon.

Metal Gear Solid to Metal Gear Solid 2


The Codec system first appears in Metal Gear Solid (MGS), and returns in all chronological sequels. MGS also marked the introduction of full voice acting during radio conversations, which would appear in all later games except those released on portable consoles.

MG2 and MGS both featured unique sequences where the player needed to look on the back of the game’s packaging to discover a crucial radio frequency, and, in the case of MGS, was required to advance the game’s story. This minor twist would become infamous among players who had rented the game; since many video game rental outlets such as Blockbuster do not provide the original packaging along with the game, the only option for these players was to use an online guide to discover the frequency. Although its original purpose was to act as an anti-piracy measure for the designers, it was vital to show players early in the game that Metal Gear Solid was a very different gaming experience than what they were used to.

Metal Gear: Ghost Babel utilizes a similar usage to MGS. However, it also includes a video upload system for operatives if transmissions given by the enemy to the central government are found.

To make the Codec screen more interactive, different features have often been added in different games. For example, in Metal Gear Solid 2 (MGS2), pressing the R1 or R2 button will allow the player to hear the main character’s thoughts, and moving the analog sticks will change the camera angle of the characters’ portraits.

Metal Gear Solid 3 to Metal Gear Solid 4
In Metal Gear Solid 3 (MGS3), the radio allows the player to view personal information about Naked Snake’s contacts (more detailed information can be unlocked by frequently calling his support team). In addition, at some points during the call, pictures are displayed showing certain subject matter (e.g., various weapons/equipment, flora/fauna, machinery, and personnel) and videos (to demonstrate where someone is to go) will pop up to explain how to proceed and/or give the player a viewpoint. The radio can also be used to remove the Alert status when contacting special hidden frequencies, discovered by interrogating guards.

In Portable Ops (MPO), the player can use the radio to recruit certain characters (i.e., Para-Medic and Sigint) by inviting them to travel to the San Hieronymo Peninsula during optional missions, and then retrieve them, or in the case of Ghost, not recruit Sokolov. The player can access radio calls via non portable radios located inside the communication base and, in the case of Ocelot, the ravine, although these require special circumstances. Both Snake and other soldiers can contact Para-Medic, Roy Campbell, Sigint, and Ghost via radio for optional conversations. However, only Snake will actually be shown speaking and giving replies to either of those characters.

The official website for Metal Gear Solid: Portable Ops Plus allows the user to contact Naked Snake using the Radio. His frequency changes each time he is contacted.

While the Codec appears in the Metal Gear Acid games, it is not accessible, nor interactive, during gameplay, and is only used by the characters during cutscenes.

The Codec was revamped for Metal Gear Solid 4 (MGS4), featuring a new screen layout and fully, realistically animated 3D models. In addition, the player can now not only fast forward conversations (a feature added in MGS2) but can skip them entirely. The player can also resume the conversation at any time during a fast forward. However, it should be noted that the 3D layout for communicating with the characters is only reserved for Otacon, Roy Campbell, and Rosemary. Other contacts such as Drebin, Rat Patrol Team 01, and Raiden’s screens will not display the characters at all, and in fact will either display static (Raiden) or the logo for the respective group (Rat Patrol and Drebin). MGS4 does not allow the player to save their progress via Codec contacts, as saving is instead relegated to the pause menu.

Hideo Kojima had desired to implement a way to only let the player see their contacts when using the radio since MGS2, although he wasn't able to implement it until MGS3, which even then, it still took until MGS4 for the main character to be audio-only in the Codec/radio calls (as MGS3 had Naked Snake still being somewhat present in the radio conversations, only somewhat out of view and part of the background).

Metal Gear Rising: Revengeance
The Codec makes a reappearance in the game Metal Gear Rising: Revengeance (MGR), possessing more Codec conversations in the game than in MGS4. Cutscene or otherwise plot-important Codec calls appear in front of Raiden while he walks automatically in the form of the holoscreen, while optional Codec calls will appear in a similar manner to previous games by being selectable from the main menu and then calling the person. MGR is the first game since MGS3 to have a radio contact assigned to save the player's progress (in this case, Courtney Collins), and to have basic bio data for each contact when spoken with. Accessing most of the Codec calls in MGR' will unlock the achievement "Amateur Radio Operator." After defeating various bosses (specifically, LQ-84i, Mistral, Monsoon, and Sundowner), they will contact Raiden posthumously via the Codec immediately afterwards for one final transmission. Unlike previous games, MGR does not actually have frequencies for the contacts, with the player instead simply selecting the them by name (a feature earlier used in the non-canon Snake's Revenge). The player cannot access the Codec during the prologue, which is only available from Chapter R-01, with Codec calls being supplied automatically in real-time, and even then, only from Boris Popov. The Codec Screen is inaccessible in Jetstream and Blade Wolf DLC, although LQ-84i, Monsoon, and Steven Armstrong do call Sam during scripted events in the former, and Mistral and Khamsin do call the LQ-84i in scripted events of the latter (the latter character in a FMV cutscene only).

Peace Walker and Ground Zeroes
In Peace Walker (PW), the radio system (referred to in-game by Naked Snake as a radio with a circuit to reverse the audio phase) was completely revamped: For instance, during the prologue, the radio can only be accessed during certain points of the mission, and thus cannot be freely used until the beginning of Chapter 1. Even then, the radio, identified as the "Codec" in the menu, will alter frequencies between each chapter (or in the case of Chapter 1 and Chapter 5, between two events), and the player will also select the radio by menu or access it by pressing the select button if it is currently assigned to the radio. In addition, because of these new features, the player cannot actually select who to contact, as the calls will be random, and in addition, the calls themselves are very short. The staple of detailed conversations in the series are instead reserved for the Briefing Files as well as the briefing/debriefing Codec calls reserved for the end of a mission. Also, the radio can be used to transmit certain commands to CO-OP partners under the CO-OP menu, and in the case of the Date with Paz mission and certain bonus radio transmissions, bolster/lower her emotional level and intimidate various enemy soldiers, respectively. In the same game, after completing some missions, there are also post-mission codec calls where Naked Snake communicates with one of the main characters. Some are replayable, such as the post-mission codec calls at the end of most of the Main Ops missions. Others, however, are one time only. Examples of the latter include calls where Kazuhira Miller informs Snake of a new function on Mother Base, his notifications on Mother Base’s renovations to a Hexagon-based design, briefings unlocked after placing Huey and Strangelove into the R&amp;D Team, ZEKE’s completion, as well as Miller informing Snake about recent events in Chapter 5 (such as EVA delivering a cassette tape, Paz and Strangelove requesting to join MSF, and notifying Snake of Zadornov’s escapes). The game Metal Gear Online also had the Codec operate in a similar manner. In addition headsets that are unlockable via the Reward Zone (which are based on the headsets used by Pieuvre Armement and Praying Mantis) allow the player to access the Codec.

In Metal Gear Solid V: Ground Zeroes, the player can, by pressing the shoulder button, can only contact Kazuhira Miller for some background details on whatever is sighted in first person view. In addition, like Peace Walker before it, detailed conversations in Ground Zeroes will be accessed via cassette tapes that are collectible throughout the game instead of via radio contacts. The Phantom Pain is also implied to have this as well, with Kojima saying this method was more impactful due to the player piecing together the story.

In-universe references
In Metal Gear Solid, Liquid asked Snake whether he "liked his sunglasses," in reference to his impersonation of Master Miller. Prior to revealing his true identity via the Codec, he physically removes the eyeware in his animated portrait displayed in the game. Since no characters possess any visual display monitors in the game, this is generally considered to be an act of fourth wall breaking. Additionally, Nastasha Romanenko makes it clear in her book In the Darkness of Shadow Moses that her communication with Snake through the Codec is exclusively via audio transmission. She only hears Snake’s voice and the game’s events due to radio equipment in her house. This was also explicitly stated by Solid Snake when he asked Otacon what does Meryl look like after losing contact with her. Liquid’s line of dialogue, however, is maintained in the Raymond Benson novelization, in which the Codec actually includes a wrist-mounted screen for video communication. It was omitted from Nastasha's book though. Adding to the confusion, Naomi's bio, included on the Metal Gear Solid: The Twin Snakes website, listed that Naomi supplied support to Solid Snake via video-communication (vidcom), further complicating the issue of whether there was supposed to be a visual for the Codec as well.

In MGS3, Para-Medic will mention that, "50 years from [the Virtuous Mission]," radios would be developed that allow the user to see who is being contacted, in an optional radio conversation. MGS4 is the first game to show the player character using the Codec with a video monitor, via the Metal Gear Mk. II, and later, the Mk. III. Only users speaking through a camera, i.e. Otacon, Campbell, and Rose, are shown in the Codec screen, whereas all other users are represented by some associated symbol; prior to obtaining the Mk. II in the game, the latter is also true for Otacon. In MGR, the Codec also utilizes visual communication, during both gameplay and cutscenes, this time using holographic displays, and in the case of the briefing portion of Abkhazia, seeing his contacts via a specialized optical implant on his right eye.

Other examples occur throughout the Metal Gear series that appear to break the fourth wall and also indicate some visual communication, though they are often used as a means of conveying gameplay information, as well as characters’ personalities, to the player:
 * Various radio personnel react as though they are aware of the protagonist’s situation, without any prior dialogue with him, such as his immediate surroundings, along with items and weapons he has procured.
 * When Snake is first introduced to Mei Ling by Codec, he remarks that she is "cute," (although some believe that it might be a reference to Mei Ling’s personality/sound of her voice) and Mei Ling winks when she talks about her frequency; she also sticks out her tongue if the player calls her on multiple occasions without saving the game.


 * Meryl always removes her balaclava when she talks to Snake by Codec.
 * Meryl hears Snake’s Codec ring even though Campbell said no one but Snake would be able to hear it.
 * Otacon hears Psycho Mantis’ mind control music while Snake is talking to Meryl.

Super Smash Bros. Brawl
The Codec also appears in Super Smash Bros. Brawl, but can only be accessed by Snake while fighting on Shadow Moses. To initiate the Codec, the player must press the taunt button for a split-second. Roy Campbell, Mei Ling, Otacon, and Slippy Toad from the Star Fox series can talk to the player about one of Snake’s opponents. In addition, although all of Snake's contacts (barring Slippy, for obvious reasons) retained their Codec portraits from Metal Gear Solid, Snake's Codec portrait was modified slightly to make him more in-line with his Metal Gear Solid 2/Super Smash Bros. Brawl appearance.

Although the Codec itself, alongside the Metal Gear franchise, does not return in Super Smash Bros. 4, its functions are retained with Pit's ability Palutena's guidance, which also requires similar methods to accessing (including using it on a specific stage [Palutena's temple in this case] and using a Smash Taunt), and also featuring the cast of the game the stage was based on, plus a character from an unrelated franchise (Palutena herself, Viridi, and Dark Pit from Kid Icarus Uprising, and Chrom from Fire Emblem: Awakening).

Contact frequencies
These are the frequencies the player can use to contact radio support personnel in the Metal Gear series.

Metal Gear

 * Big Boss - 120.85 (later 120.13)
 * Schneider - 120.79 (later 120.26)
 * Diane - 120.33 (later 120.91)
 * Jennifer - 120.48
 * FOXHOUND HQ - 120.13 (ending)
 * KNK Radio - 120.77 (ending)



Metal Gear 2: Solid Snake

 * Music - 140.07
 * Colonel Campbell - 140.85 (later 140.66 and then 140.24)
 * Master Miller - 140.38
 * Johan Jacobsen - 140.40
 * Kio Marv - 140.51
 * Holly White - 140.15 (later 140.76)
 * Drago Pettrovich Madnar - 140.82
 * George Kasler - 140.93
 * Your #1 Fan/Charlie - 140.00
 * Gray Fox - 140.27

Metal Gear Solid
''The Staff Message frequency has different effects varying in language. In Japanese, it displays a message. In English, it plays a remix of three different songs: "Discovery," "Zanzibar Breeze," and "Theme of Solid Snake." Keep in mind that both versions are only in the Integral version of the game.''
 * Staff Message - 140.07 (Japan only)
 * Meryl Silverburgh - 140.15
 * Deepthroat - 140.48
 * Staff Message - 140.66 (Japan only)
 * Colonel Campbell/Naomi Hunter/Jim Houseman - 140.85
 * Mei Ling (save) - 140.96
 * Otacon/Sniper Wolf - 141.12
 * Nastasha Romanenko - 141.52
 * "Master Miller"/Liquid Snake - 141.80



Metal Gear: Ghost Babel

 * Colonel Campbell - 140.85
 * Mei Ling - 140.96
 * Weasel - 141.80
 * Brian McBride - 141.52
 * Chris Jenner - 140.25
 * No. 4 - 141.62
 * IdeaSpy 2.5

Metal Gear Solid 2: Sons of Liberty
Tanker
 * Otacon - 141.12
 * Otacon (save) - 140.96

Plant
 * Richard Ames - 140.72
 * Colonel - 140.85
 * Rosemary (save) - 140.96
 * President Johnson - 141.37
 * Iroquois Pliskin/Solid Snake - 141.80
 * Peter Stillman - 140.25
 * Mr. X/Olga Gurlukovich - 140.48
 * Emma Emmerich - 141.52
 * Otacon - 141.12

Metal Gear Solid 3: Snake Eater

 * Major Tom/Major Zero - 140.85
 * Para-Medic - 145.73
 * The Boss - 141.80 (Virtuous Mission only)
 * Para-Medic (save) - 140.96
 * Sigint - 148.41
 * EVA - 142.52
 * Groznyj Grad cell door - 144.75

Healin’ Tracks
 * 140.01 - "Salty Catfish" / 66 Boys (Very Easy/Easy)
 * 145.83 - "Salty Catfish" / 66 Boys (Normal)
 * 146.07 - "Salty Catfish" / 66 Boys (Hard)
 * 141.42 - "Salty Catfish" / 66 Boys (Extreme)
 * 140.52 - "Rock Me Baby" / 66 Boys (Very Easy/Easy)
 * 146.65 - "Rock Me Baby" / 66 Boys (Normal)
 * 143.83 - "Rock Me Baby" / 66 Boys (Hard)
 * 148.66 - "Rock Me Baby" / 66 Boys (Extreme)
 * 141.24 - "Sea Breeze" / Sergei Mantis (Very Easy/Easy)
 * 142.09 - "Sea Breeze" / Sergei Mantis (Normal)
 * 145.72 - "Sea Breeze" / Sergei Mantis (Hard)
 * 145.18 - "Sea Breeze" / Sergei Mantis (Extreme)
 * 142.94 - "Pillow Talk" / Starry.K (Very Easy/Easy)
 * 148.96 - "Pillow Talk" / Starry.K (Normal)
 * 144.25 - "Pillow Talk" / Starry.K (Hard)
 * 140.16 - "Pillow Talk" / Starry.K (Extreme)
 * 144.06 - "Jumpin’ Johnny" / Chunk Raspberry (Very Easy/Easy)
 * 144.86 - "Jumpin’ Johnny" / Chunk Raspberry (Normal)
 * 147.96 - "Jumpin’ Johnny" / Chunk Raspberry (Hard)
 * 148.78 - "Jumpin’ Johnny" / Chunk Raspberry (Extreme)
 * 147.08 - "Surfing Guitar" / 66 Boys (Very Easy/Easy)
 * 148.39 - "Surfing Guitar" / 66 Boys (Normal)
 * 141.59 - "Surfing Guitar" / 66 Boys (Hard)
 * 146.45 - "Surfing Guitar" / 66 Boys (Extreme)
 * 147.59 - "Sailor" / Starry.K (Very Easy/Easy)
 * 143.32 - "Sailor" / Starry.K (Normal)
 * 143.97 - "Sailor" / Starry.K (Hard)
 * 142.42 - "Sailor" / Starry.K (Extreme)
 * 149.53 - "Don’t Be Afraid" / Rika Muranaka (Very Easy/Easy)
 * 141.85 - "Don’t Be Afraid" / Rika Muranaka (Normal)
 * 144.63 - "Don’t Be Afraid" / Rika Muranaka (Hard)
 * 149.39 - "Don’t Be Afraid" / Rika Muranaka (Extreme)

Note: Calling any one of the Healin' Tracks and all of the Healin' Tracks in the HD version will unlock the achievements/trophies Serenity Now (a subtle pun of the film Apocalypse Now) and Tune-In Tokyo, respectively.

Cancel Alert Fire Support Request Frequency locks
 * 146.20 - Dolinovodno (Hard)
 * 142.65 - Dolinovodno (Extreme)
 * 143.03 - Bolshaya Past South (Very Easy/Easy)
 * 147.11 - Bolshaya Past South (Normal)
 * 146.91 - Bolshaya Past South (Hard)
 * 144.52 - Bolshaya Past South (Extreme)
 * 149.46 - Bolshaya Past Base (Normal)
 * 140.61 - Ponizovje West (Normal)
 * 145.42 - Ponizovje West (Hard)
 * 149.75 - Ponizovje Warehouse: Exterior (Very Easy/Easy)
 * 149.63 - Ponizovje Warehouse (Very Easy/Easy)
 * 141.45 - Ponizovje Warehouse (Normal)
 * 142.48 - Ponizovje Warehouse (Hard)
 * 143.72 - Ponizovje Warehouse (Extreme)
 * 149.90 - Graniny Gorki Lab 1F/2F (Very Easy/Easy)
 * 145.07 - Graniny Gorki Lab 1F/2F (Extreme)
 * 144.87 - Graniny Gorki Lab B1 East (Hard)
 * 145.31 - Graniny Gorki Lab B1 East (Extreme)
 * 148.87 - Svyatogornyj West (Very Easy/Easy)
 * 142.79 - Svyatogornyj West (Normal)
 * 145.59 - Svyatogornyj West (Hard)
 * 144.28 - Svyatogornyj West (Extreme)
 * 146.59 - Svyatogornyj East (Very Easy/Easy)
 * 148.04 - Svyatogornyj East (Normal)
 * 142.03 - Svyatogornyj East (Hard)
 * 147.79 - Svyatogornyj East (Extreme)
 * 140.94 - Krasnogorje Mountain Base (Hard)
 * 148.54 - Krasnogorje Mountain Base (Extreme)
 * 145.94 - Krasnogorje Mountainside (Very Easy/Easy)
 * 146.67 - Krasnogorje Mountainside (Normal)
 * 140.15 - Krasnogorje Mountaintop (before EVA; Very Easy/Easy)
 * 141.98 - Krasnogorje Mountaintop (before EVA; Normal)
 * 140.58 - Krasnogorje Mountaintop (after EVA; Hard)
 * 148.26 - Krasnogorje Mountaintop (after EVA; Extreme)
 * 143.16 - Groznyj Grad 1F Southwest Section (Very Easy/Easy)
 * 147.54 - Groznyj Grad 1F Southwest Section (Hard)
 * 147.49 - Groznyj Grad 1F Northwest Section (Very Easy/Easy)
 * 140.47 - Groznyj Grad 1F Northwest Section (Extreme)
 * 141.53 - Groznyj Grad 1F Northeast Section (Normal)
 * 141.17 - Groznyj Grad 1F Northeast Section (Extreme)
 * 144.40 - Groznyj Grad 1F Southeast Section (Normal)
 * 146.08 - Groznyj Grad 1F Southeast Section (Hard)
 * 143.94 - Groznyj Grad Weapons Lab East Wing (Very Easy/Easy)
 * 144.61 - Groznyj Grad Weapons Lab East Wing (Normal)
 * 147.65 - Groznyj Grad Weapons Lab East Wing (Hard)
 * 144.14 - Groznyj Grad Weapons Lab East Wing (Extreme)
 * 140.73 - Bolshaya Past South (Very Easy/Easy)
 * 141.62 - Bolshaya Past South (Normal)
 * 147.23 - Bolshaya Past South (Hard)
 * 146.14 - Bolshaya Past South (Extreme)
 * 148.63 - Bolshaya Past Base (Hard)
 * 148.17 - Bolshaya Past Base (Extreme)
 * 145.28 - Ponizovje West (Very Easy/Easy)
 * 142.12 - Ponizovje West (Normal)
 * 140.36 - Ponizovje West (Hard)
 * 143.20 - Ponizovje West (Extreme)
 * 143.89 - Ponizovje Warehouse: Exterior (Very Easy/Easy)
 * 147.32 - Ponizovje Warehouse: Exterior (Normal)
 * 144.19 - Ponizovje Warehouse: Exterior (Hard)
 * 148.98 - Ponizovje Warehouse: Exterior (Extreme)
 * 144.03 - Ponizovje Warehouse (Very Easy/Easy)
 * 148.56 - Ponizovje Warehouse (Normal)
 * 142.91 - Ponizovje Warehouse (Hard)
 * 140.22 - Ponizovje Warehouse (Extreme)
 * 143.61 - Graniny Gorki Lab Exterior Yard (Very Easy/Easy)
 * 146.74 - Graniny Gorki Lab Exterior Yard (Normal)
 * 149.84 - Graniny Gorki Lab Exterior Yard (Hard)
 * 147.82 - Graniny Gorki Lab Exterior Yard (Extreme)
 * 144.93 - Svyatogornyj West (Very Easy/Easy)
 * 141.31 - Svyatogornyj West (Normal)
 * 141.79 - Svyatogornyj West (Hard)
 * 147.04 - Svyatogornyj East (Very Easy/Easy)
 * 149.29 - Svyatogornyj East (Normal)
 * 142.86 - Svyatogornyj East (Hard)
 * 145.80 - Svyatogornyj East (Extreme)
 * 143.98 - Krasnogorje Mountain Base (Very Easy/Easy)
 * 145.68 - Krasnogorje Mountain Base (Normal)
 * 149.52 - Krasnogorje Mountain Base (Hard)
 * 141.03 - Krasnogorje Mountain Base (Extreme)
 * 144.39 - Krasnogorje Mountainside (Very Easy/Easy)
 * 147.90 - Krasnogorje Mountainside (Normal)
 * 149.12 - Krasnogorje Mountainside (Hard)
 * 146.46 - Krasnogorje Mountainside (Extreme)
 * 143.56 - Krasnogorje Mountaintop (before EVA; Very Easy/Easy)
 * 140.09 - Krasnogorje Mountaintop (before EVA; Normal)
 * 142.29 - Krasnogorje Mountaintop (after EVA; Hard)
 * 145.99 - Krasnogorje Mountaintop (after EVA; Extreme)
 * 149.06 - Zaozyorje East (Very Easy/Easy)
 * 146.33 - Zaozyorje East (Normal)
 * 148.31 - Zaozyorje East (Hard)
 * 146.82 - Zaozyorje East (Extreme)
 * 148.13 - Groznyj Grad Weapons Lab East Wing 1F Eastern Door (Very Easy/Easy /Normal)
 * 144.41 - Groznyj Grad Weapons Lab East Wing 1F Eastern Door (Hard)
 * 141.06 - Groznyj Grad Weapons Lab East Wing 1F Eastern Door (Extreme)
 * 147.86 - Groznyj Grad Weapons Lab East Wing 2F Northern Door (Very Easy/Easy/Normal/Hard)
 * 149.48 - Groznyj Grad Weapons Lab East Wing 2F Northern Door (Extreme)
 * 145.86 - Groznyj Grad Weapons Lab East Wing 1F Western Door (Very Easy/Easy/Normal)
 * 146.95 - Groznyj Grad Weapons Lab East Wing 1F Western Door (Hard)
 * 142.81 - Groznyj Grad Weapons Lab East Wing 1F Western Door (Extreme)
 * 143.45 - Groznyj Grad Weapons Lab East Wing 2F Southern Door (Very Easy/Easy/Normal)
 * 140.30 - Groznyj Grad Weapons Lab East Wing 2F Southern Door (Hard)
 * 142.57 - Groznyj Grad Weapons Lab East Wing 2F Southern Door (Extreme)

Metal Gear Acid

 * 145.11 - Roger McCoy

Metal Gear Solid: Portable Ops

 * 140.85 - Roy Campbell/various soldiers recruited by Snake
 * 143.15 - Prisoner Evacuation
 * 145.73 - Para-Medic
 * 148.41 - Sigint
 * 144.73 - Ghost
 * 145.75 - Frequency lock key
 * 147.42 - Frequency lock key
 * 148.51 - Frequency lock key
 * 145.62 - Frequency lock key (Saturn V documents)
 * 140.02 - HQ (Town)
 * 146.78 - HQ (Town, multiple revisits)
 * 141.23 - Ocelot
 * 145.25 - EVA



Super Smash Bros. Brawl

 * Colonel Campbell - 140.85
 * Mei Ling - 140.96
 * Otacon - 141.12
 * Slippy Toad - 140.85

A full list of the Codec conversations from Super Smash Bros. Brawl can be found here.

Metal Gear Solid 4: Guns of the Patriots

 * Otacon - 141.12
 * Rosemary - 147.79
 * Rat Patrol Team 01 - 140.15
 * Roy Campbell - 140.85
 * Raiden - 141.80
 * Drebin - 148.93

''While the player can call Otacon and Rosemary almost anytime they please, the rest of the contacts will only call them at certain points of the storyline. On that note, the contacts that only call at certain parts of the story (barring Campbell) also never show their face.''

Metal Gear Solid: Peace Walker
The radio is referred to as the Codec in the menu screen and the frequencies change during each chapter.

A Country Without an Army

Eastern Limon:
 * Miller: 145.38
 * Paz: 140.11

Mt. Irazu Area:
 * Miller: 144.17
 * Paz: 143.16
 * Amanda: 145.66
 * Chico: 140.96

The Phantom Hero
 * Miller: 142.03
 * Paz: 144.09
 * Amanda: 145.72
 * Chico: 143.42
 * Huey: 146.74
 * Cécile: 140.89

A Nation Reborn
 * Miller: 147.75
 * Amanda: 141.46
 * Chico: 140.08
 * Huey: 144.21
 * Cécile: 145.74

The Illusion of Peace
 * Miller: 144.16
 * Paz: 144.16
 * Amanda: 140.90
 * Chico: 143.47
 * Huey: 146.88
 * Cécile: 147.65

Outer Heaven

Zadornov missions:
 * Miller: 145.38
 * Paz: 140.11
 * Amanda: 144.42
 * Chico: 143.63
 * Cécile: 146.95
 * Strangelove: 142.52

ZEKE Battle:
 * Miller: 149.57
 * Amanda: 144.44
 * Chico: 140.57
 * Huey: 143.11
 * Cécile: 146.52
 * Strangelove: 145.82

Other
 * The End: 000.00

Metal Gear Rising: Revengeance
Main story:
 * Boris Vyacheslavovich Popov
 * Kevin Washington
 * Courtney Collins
 * Doktor
 * Blade Wolf (Chapter R-02 onward)
 * LQ-84i (Chapter R-01, post-battle only)
 * Sunny (Chapter R-07 only)
 * George (Chaper R-03, opening cutscene only)
 * Mistral (Chapter R-01, post-battle only)
 * Monsoon (Chapter R-03, post-battle only)
 * Sundowner (Chapter R-04, post-battle only)

Jetstream DLC:
 * LQ-84i (post-battle only)
 * Monsoon (pre-entry to Japanese garden reception only)
 * Steven Armstrong (elevator only)

Blade Wolf DLC:
 * Mistral
 * Khamsin (cutscene and post-battle only)

Metal Gear Solid V: Ground Zeroes

 * Kazuhira Miller
 * Huey Emmerich (cutscene only)

Metal Gear Solid V: The Phantom Pain

 * Ocelot

Notes and references
Codec