Group 4 EAM/Claude Draft
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This subject of this article has no known official name. This article covers a subject which has not been named and/or discussed in unclassified military documents. Group 4 EAM/Claude Draft is a theoretical or proposed name. |
Group 4 EAMs (also called Group 4 messages) are those EAMs that begin with what HFGCS monitors have designated as Group 4 prefixes. A Group 4 prefix is a two character code identified through characteristic behavioral patterns observed across messages with that prefix: extended message lengths ranging from 36 to 292 characters (with Group 4 being the only category that never produces 30 character messages), extremely high prevalence of embedded repeated character sequences (particularly repeated tetragrams such as FFFF, XXXX, ZZZZ appearing in approximately 60% of messages), consistent absence of addressee designations, and concentration at specific high character counts suggesting structured internal formatting. Messages with Group 4 prefixes constitute the longest and most structurally complex category of EAMs on the High Frequency Global Communications System (HFGCS), representing approximately 3% of total traffic and making them equally rare as Group 3 messages.
The Group classification system derives from observed message behavior rather than official designation. When examining EAM traffic, monitors note that for certain periods of time, some prefixes will appear exclusively on long messages with prevalent repeated character sequences and no addressees, patterns that immediately distinguish them from all other categories. Those messages can be identified as EAMs with Group 4 prefixes, and therefore categorized as Group 4 EAMs. The extended lengths and high information density distinguish Group 4 from all other categories, while the prevalence of repeated character patterns (appearing in approximately 60% for single character repetitions and 38% for multi character sequences) provides the most pronounced structural signature of any EAM group.
Defining Characteristics
Group 4 messages are distinguished by several consistent structural features that manifest across all documented transmissions. These messages are consistently longer than other EAM groups, with the most common lengths being 142, 120, 164, 68, 50, and 216 characters. Messages at 142 characters are most frequent, representing 18% of Group 4 traffic, while the documented range extends from 36 to 292 characters, though the vast majority fall between 50 and 216 characters.
Approximately 60% of Group 4 messages contain repeated single character sequences of four or more characters, such as FFFF, XXXX, RRRR, and ZZZZ. These repetitions appear embedded throughout the message structure rather than at fixed positions, with this prevalence representing the highest rate of any repetition pattern across all EAM groups. Common repeated patterns include FFFF (62 occurrences), 2222 (58), IIII (56), XXXX (53), LLLL (45), TTTT (43), CCCC (40), BBBB (40), OOOO (38), RRRR (37), VVVV (36), WWWW (34), 3333 (33), ZZZZ (32), HHHH (32), and 7777 (32).
Examples of Group 4 messages with repeated sequences demonstrate this characteristic pattern. The message `BA4GDLLNXPR7E6ZFU2XLYTRYGBF2LE44GXJSEYVS7ZZZZR6IWXGV635VPZN3D3KAAAAFIL4HEYN37BGOIOHFJRRRRQVFYFG2CR4JVUEUKGKKKKKTN2WHHZNDDC5TNYLN2LRQQHTX75Q5IE` at 142 characters contains multiple embedded repeated sequences including ZZZZ, AAAAA, RRRR, and KKKKKK. Similarly, the 120 character message `BA5PZRQ3J42QLI2PYJIE2GW2Z5F6I6K6S3H2KKB2UVVVVRFHYTICTDOP3G5575GVVVVRN3RZFZFZCSTPDDMDCBBBBMSOJCWC3VWFSIPPAPIWWWWR7PT4NBXA` displays repeated sequences of VVVVV, BBBB, and WWWWW, while the message `BAVKGYL7IR2XBICEYUJE2JL2Z5FQ6NCNN3UBBHUKRVVVVRFHYCTDCTUP7S5DUSJVVVVRN3RXZ2OCZSGMD7VM7BBBBMSOJ4CXVXZFHBPVHVIWWWWR75UINAETWXCSRLTCOAAAA4YKAZRERM` at 142 characters contains VVVVV, BBBB, WWWWW, and AAAA.
Additionally, approximately 38% of Group 4 messages contain repeated multi character sequences of three or more characters, similar to the pattern observed in Group 3 Messages. This shared characteristic suggests both groups may employ related encoding or formatting schemes. The function of these repeated sequences is unknown but may serve as delimiters, error detection codes, formatting markers, or structural indicators within the message architecture.
Group 4 messages never include "FOR [CALLSIGN]" specifications, maintaining like Group 3 Messages a pattern of broadcast without addressee designations. Unlike Groups 1, 2, and 3, no documented Group 4 message has been exactly 30 characters long, providing an absolute distinction that is unique to Group 4 and serves as a reliable negative identifier. If a message is 30 characters, it is definitively not Group 4. The shortest documented Group 4 message is 36 characters, establishing a lower bound that distinguishes Group 4 from shorter message groups.
Prevalence
Group 4 messages are rare, constituting approximately 3% of total HFGCS traffic. This places Group 4 at equal rarity with Group 3 Messages, and both groups combined represent only about 6% of total EAM broadcasts compared to Group 1's dominance at approximately 66% and Group 2's approximately 26%.
Group 4 activity appears more consistent than Group 3's sporadic pattern. While Group 3 prefixes often appear briefly then disappear for extended periods, Group 4 prefixes show more sustained usage, though still less frequent than the daily presence of Groups 1 and 2.
Length Distribution
Group 4 messages show distinctive length clustering at specific high character counts that distinguish them from all other EAM categories. The concentration at 142 characters is particularly distinctive, with this length alone accounting for nearly one fifth of all Group 4 messages at 18% of Group 4 traffic. Other prominent lengths include 120 characters at 8% of Group 4 traffic, 164 characters at 7%, 68 characters at 6%, 50 characters at 10%, and 216 characters at 5%. Secondary common lengths including 166, 172, 92, 62, 246, 56, 108, and 60 characters each appear in 2 to 5% of Group 4 traffic.
The prevalence of lengths that are multiples of common block sizes such as 50, 60, 68, 120, and 142 suggests these messages follow structured internal formatting with specific capacity requirements. The longest documented Group 4 message was 292 characters, representing an outlier in the overall distribution but demonstrating the upper bounds of Group 4 message capacity.
Identification Methodology
Group 4 messages are among the easiest to identify due to their distinctive length profile and structural characteristics. Any message longer than 78 characters with no addressee is very likely Group 4, as Group 3 rarely exceeds this length. Messages at 142, 120, or 164 characters are almost certainly Group 4.
The presence of repeated four or more character single letter sequences such as FFFF, XXXX, and ZZZZ strongly indicates Group 4. While Group 3 also contains repeated sequences, Group 4's prevalence at 60% compared to 40% and tendency toward longer repetitions is distinctive. Messages longer than 163 characters are definitively Group 4, as this exceeds the maximum documented length for Group 2 at 163 characters and Group 3 at 78 characters.
A prefix can be identified as Group 4 if it is consistently used for messages in the 50 to 292 character range, never appears with addressee specifications, and frequently contains repeated character patterns. The distinctive length profile makes Group 4 the most reliably identifiable group after Directed EAMs, which are immediately apparent through their addressee specifications.
Transmission Error Rate
Group 4 messages show the highest rate of transmission errors and "DISREGARDED" broadcasts among all EAM groups. The combination of extended length and complex character patterns increases the likelihood of operator error during voice transmission. Common error patterns include transmission aborted mid message, operator disregards after realizing an error during first or second reading, signal loss during extended transmission, and character misreads requiring correction or restart. This elevated error rate is an inevitable consequence of transmitting 100 to 200 or more character alphanumeric sequences via voice communication and does not appear to indicate any operational deficiency.
Prefix Patterns
Group 4 prefix behavior shows more consistency than Group 3 but remains less frequent than Group 1 or Group 2. Commonly observed Group 4 prefixes include JC with 67 documented messages, MN with 46, BH with 42, JO with 31, 6K with 24, BW with 23, PC with 22, RO with 21, BJ with 21, BV with 19, LO with 18, ET with 17, YP with 14, BA with 8, and H5 with 8.
During continuous monitoring from June 2023 through February 2024, Group 4 prefixes appeared intermittently but showed more sustained usage than Group 3 prefixes. For example, the 6K prefix was active across June through July 2023, and the JC prefix showed extended usage from July through September 2023. Whether Group 4 operates on a rotation schedule similar to Groups 1 and 2 or represents demand driven usage tied to specific operational requirements remains unclear. The more consistent appearance pattern compared to Group 3 suggests Group 4 may serve ongoing operational needs rather than exercise specific or condition dependent purposes.
Relationship to Other Groups
Group 4 exists within a four group EAM taxonomy and shows particularly strong structural similarities to Group 3. Both Group 3 at 40% and Group 4 at 38% show nearly identical rates of embedded repeated multi character sequences of three or more characters. Additionally, Group 4's 60% rate of single character repetition of four or more characters like FFFF represents a related but more pronounced pattern. This shared emphasis on repeated sequences suggests both groups may employ related encoding or formatting schemes for specialized operational purposes.
The primary distinction is length. Group 3 Messages cluster at shorter lengths with 22 to 48 characters typical and 78 maximum, while Group 4 messages are consistently longer with 50 to 216 characters typical and 292 maximum. This length distinction appears absolute, with no overlap in the typical operating ranges.
Group 1 Messages are always 30 characters, never have addressees, constitute approximately 66% of traffic, and rarely contain repeated sequences at 1%. Group 2 Messages have variable lengths from 30 to 163 characters, frequently include addressees, constitute approximately 26% of traffic, and show moderate repetition rates at 11%.
All four groups operate independently with separate prefix systems. The strong structural similarity between Groups 3 and 4, combined with their comparable rarity at approximately 3% each and shared absence of addressees, suggests these groups represent specialized communication categories distinct from the baseline Group 1 traffic and directed Group 2 communications.
Operational Context
The distinctive characteristics of Group 4 messages, including extended lengths, embedded repeated sequences, structured length clustering, and absence of addressees, suggest this group serves a specialized operational purpose requiring high information density. The concentration at specific lengths, particularly 142, 120, and 164 characters, suggests standardized message templates with predetermined capacity requirements. The prevalence of repeated character sequences at 60% with four or more character single letter repetitions and 38% with three or more character multi character sequences may indicate formatting markers, error detection mechanisms, or structured data fields within the message architecture.
The higher error rate during transmission indicates that Group 4's extended length and complexity represent operational trade offs, where these messages carry more information but at the cost of increased transmission difficulty and potential for errors. The shared structural characteristics with Group 3, including repeated sequences and specialized formatting, combined with the length distinction suggests Groups 3 and 4 may represent short form and long form variants of a related communication architecture serving similar operational purposes.
However, without access to message content or operational documentation, the specific purpose of Group 4 messages remains speculative.