[Hallicrafters] 5-letter signals

[howard holden]

I was a CW op in the Navy from 66 to 70 (NAW and NGR). Copied far more than my share of crypto traffic from a variety of ships worldwide. 

All five letter groups which were part of a message text were letters only. Not sure of why 5 letters, but it made for a neat, organized copy by a good operator - 10 groups per line, double spaced, 10 lines per page. If a group was messed up, you could go back to the sending station and ask for a repeat of group # XXX, easily identified with the 10 group lines. 

Also, all offline crypto messages started out with a 5 character number. For US stations, the numbers were 1, 3, 5, 7, and 9, the order chosen by the encrypting system, and the group always started and ended with #5, for NATO stations the number group was even numbers only. That was followed by five phonetic characters (alfa, juliette, etc.). That preamble of the number group and the five phonetics set the decrypting configuration, and those were always part of the total group count of the message. The message then ended with the five number group repeated. 

This format was used for all Navy offline crypto.

A crypto message in delivery format might look like this:

NGR DE NC (RANDOM TWO LETTER CALLSIGN, CHOSEN BY THE SHIP OPERATOR)
- P P - 030500Z JAN 05
GR42
BT
57395 BRAVO CHARLIE FOXTROT NOVEMBER ECHO    EDMGT HGIER BVOOQ RSMKY 
(BALANCE OF GROUPS, 10 PER LINE) 57395
BT

When a message was set for encoding, all numbers were made into words (four, five, nineteen, etc.) so that you only needed letter characters. When the message was decoded, there were no spaces between words as it came off the crypto box, all ran together, so the crypto operator would have to sort the spacing out in a logical fashion. 

A message from a ship which in normal format looks like this:

P P 020151Z MAY 07
FM USS SEACAT
TO COMSUBRON 12
BT
UNCLAS E F T O
CHECK TWO FOUR SUBMARINE SEACAT
BT



After having been received in encrypted 5 letter groups then decrypted, it would look like this from the crypto:

P P Z E R O T W O Z E R O O N E F I V E O N E Z U L U M A Y Z E R O S E V E N F R O M U S S S E A C A T T O C O M S U B R O N O N E T W O B R E A K U N C L A S E F T O C H E C K T W O F O U R S U B M A R I N E S E A C A T B R E A K

The crypto op then would have to reassemble it into an "officer-readable" form as above. 

There was also a "quickie" crypto system called "NUCO", used only for fast exchanges between operators. It used a two letter group, and was not considered secure enough for normal traffic. But that's another story....


Howie WB2AWQ RM2 USN, 1966-1970