A6-2 (P) EEW/mc

31 October 1941

From:Commandant, Thirteenth Naval District. To:Radioman-in-Charge, U. S. Naval Radio Direction
Finder Station, Imperial Beach, California.
Radioman-in-Charge, U. S. Naval Radio Direction
Finder Station, Farallon Islands, California.
Radioman-in-Charoe, U. S. Naval Radio Direction
Finder Station, Point St. George, via Crescent
City, California.
Commanding Officer, U. S. Naval Radio Station,
Bainbridge Island, Port Blakely, Washington.
Commanding Officer, U. S. Naval Air Station,
Sitka, Alaska.

Subject:Operating Instructions, Strategic Direction Finder

Reference:(a) Enclosure (A) to Com14 SECRET Ltr., Serial Z-2051,
dated 8 October 1941, addressed to had-Pacific
Net Stations.

Enclosure:(A) General Instructions for Strategic Direction Finder
Station Operators (pages 1 to 10 inclusive).

1.Reference (a), promulgated by the Commandant, Fourteenth Naval District, was specifically written for the Mid-Pacific Strategic Net, but portions thereof are considered to be excellent basic instructions for strategic direction finder operators of the West Coast Strategic Net as well, and such portions are incorporated in enclosure (A),

2.It is suggested that the Commandants concerned require a regular accounting of these SECRET instructions by the Radiomen-in-Charge of the direction finder stations as in the case of registered publications.

3.It is hereby certified that the originator considers it to be impracticable to phrase this document in such a manner as will permit a classification other than secret. It is essential that this letter be forwarded with the least possible delay and its transmission by registered mail within the continental limits of the United States is necessary and is authorized.


Guy Davis
Chief of Staff

Copy to:
CNO (enclosure #6 )
Comll (enclosure #7)
Com12 (enclosure #8)
Com14 (enclosure #9)


1.  The following GENERAL INSTRUCTIONS are prepared for the information
    and guidance of direction finder operators in the West Coast High
    Frequency Strategic Direction Finder Net and are to be considered as
    supplementary to the OPERATING INSTRUCTIONS, NUMBER 1, issued on
    18 August 1941, or modification thereto as issued from time to time.

2.  These GENERAL INSTRUCTIONS are to be read and thoroughly understood
    by all personnel in the West Coast Strategic Net who are engaged in
    radio direction finder work and who are assigned to such duties,
    either temporarily or permanently. Hereafter, the word "stations"
    will apply to the individual direction finder stations of the West
    Coast High Frequency Direction Finder Net, and "Net Control" will
    indicate the Net Control Officer at the District Communication Office,
    Thirteenth Naval District, Seattle, Washington.


The mission of the West Coast Strategic Net is to perfect efficiency in the obtaining of maximum comrmnication intelligence of the enemy through the operation of a high frequency direction finder organization. Task assignments will be made from time to time, giving specific directives as to frequencies to be covered and other details necessary to carry out these assignments, and it must be borne in mind at all times that, as the efficiency of the Net increases, its value for strategic purposes increases in direct proportion to its efficiency.


Specific station assignments may be given the Net either by mail or by dispatch as time or occasion dictates, and will be forwarded through the Net Control to the stations of the Net. It is important to remember that a task assignment does not of itself cancel any previous assignments unless it specifically states the fact of cancellation of previous assignments or modification thereof.

Enclosure (A) to Com13 SECRET SERIAL #203035

- 1 -

Serial No.  13  


2. Continued.


(1) For all stations provided with a complement of four or more
radiomen, it is directed that a 24-hour watch be maintained. Any necessary deviation from this continuous watch will be communicated to the Net Control at once by dispatch, using appropriate code in the interests of security. The false conception among some operators that the "dark" optimum period of good signals is the only important watch period must be eliminated and the following axiom substituted: EVERY RADIO SIGNAL COMING UNDER THE NET TASK ASSIGNMENT MUST BE OBSERVED AND ANALYZED BY THE STATIONS OF THE WEST COAST NET TO THE FULLEST EXTENT OF MATERIAL AND PERSONNEL LIMITATIONS, REGARDLESS OF THE TIME OF THE DAY.

(2) The only deviation allowable from this rule will be under
conditions where the task assignment directs that certain schedules, given frequencies, individual call letters, or groups of calls are to be observed during stated time intervals.

(3) The stations in the Net are considered by the Net Control
as being radio intelligence intercept stations as well as direction finder stations, and all associated data in connection with bearings taken should be logged with this idea in mind. Frequency, time (always in GCT), peculiarities of signals, and if possible, an exact transcript of the message on which the bearing was taken, together with any other pertinent data should be logged. The following fictitious example illustrates the possibilities involved in a hypothetical situation:

Faint signals on 6935
kc 0100 using numeral
2 character calls.
Estimated seven sta-
tions on that circuit.
1- Frequency identified from previous
known information as submarine

2- Assumption made that at least a
squadron of enemy submarines are
engaged in intercommunication.

Enclosure (A) to Com13 SECRET SERIAL #203035

- 2 -


2. Continued.


(3) Continued.
3- Further observations now made
possible. Other stations in Net
advised to observe, after which

4- One station uncovers same number
o units transmitting on same
frequencies at 0100 and 1500 on two
successive days, after which

5- It is fairly definite that at least
seven submarines are at large in
separated areas, which communicate
with their commander on schedule
at least twice daily.

6- Coordinated bearings by all sta-
tions in the Net enable fixes to
be made locating approximate posi-
tions for further tracking by
aircraft or surface scout.

(4) Up to point 5 no bearings were obtained, but valuable
information has been obtained and, what is more important, provisions for definite future observations of these particular ships have been made with a minimum of effort (observing 6935 kc at 0100 and 1500 GCT). The Net Control does not expect that every observation by individual stations of faint signals will be forwarded to Net Control, but does expect that operators will use initiative and judgment in such matters, and that every direction finder operator will realize the important duty he is performing as an integral part of a vital radio intelligence network, and further, that close cooperation and continuity of effort in the Net must first be realized at each station between operators.

Enclosure (A) to Com13 SECRET SERIAL #203035

- 3 -


2. Continued.


Greenwich Civil Time will be kept by all stations of the West Coast Net. all times and dates reported in any dispatch or written report will be understood to be GCT unless otherwise indicated. THIS IS IMPORTANT AND MUST BE STRICTLY ADHERED TO IN ORDER TO AVOID POSSIBLE CONFUSION.


(1) The Net Control considers the various radio intelligence
components normally obtainable by the stations of the Net in the following general order of importance:

(a) Radio Call and Bearing.     A04 - 095 degrees
(b) Radio Frequency. 7000 kc
(c) Compromising Informa-
"AE6..... 3HAN" received by direction finder operator should be reported to the effect that AE6 appears to be same as 3HAN.
(d) Circuit Information. 3 stations on circuit, Controlling station, etc.
(e) Caliber of Bearing. RED, WHITE, BLUE or BLACK.
(f) Time of Bearing. 1530 (GCT understood)

Enclosure (A) to Coml3 SECRET SERIAL #203035

- 4 -

2. Continued. e. RELATIVE VALUES OF IIVfORPLATIOId OBTAINED. (Continued) (2) The above should be used as a guide only, particularly since operating instructions may designate some specific order in which to submit information to Net Control. While the primary mission o a direction finder station will never permit the direction finder bearings and calls to be relegated to secondary importance, the supplying of pertinent information in the absence o reliable bearings and well-defined calls may sometimes serve the same purpose, or at least help complete the chain of information needed to identify the source of the observed signal. Frequencies, when accurately observed and reported within 5 kilocycles, should definitely indicate the type of ship or the subdivision of fleet involved. lmC'1" (4) VJHEN NEVV CALLS ARE HEA?tD OR AN`f ACTIVITIES ARE NOTICED WHICH ARE NOT NOMIL TO THE FREQUENCIES BEING GUARDED THE DIRECTION FIPdDER OPERATOR vILL RECORD AND FORWARD THIS DATA TO NET CONTROL, TOGETHER tiIITH ANY BITS OF IIdFOR.^W^1ION THAT MAY ASSIST IN THE IDENTIFICATION OF THE STATION OBSERVED. (5) The following are examples of helpful information: (a) The fact that observed vessel appears at scheduled times. (b) Type and quality of signal, circuit discipline, operatorst peculiarities to indicate combatant ship, naval auxiliary, plane, or type o vessel or nationality. (c) The controlling station and number of stations observed on one frequency that appear to be in one organization. (d) The appearance of the same radio call on more than one frequency, indicating possible shore station or flagship. Enclosure (A) to Co>_213 SEMiT SERIAL #203035 GENERAL IhSTRUOTIOidS FC'i DIRECT I02; i~i:ID'ER STA^1IO:I OPiSPJ.'_10?:S o ~',e National qrchives-pacific Alaska Region (Seattle) GENERAL _INSTRUCTIONS FOR STRATEGIC DIRECTION FINDER STATION OPERATORS 2. Continued. e. RELATIVE VALUES OF INFORMATION OBTAINED. (Continued) (6) The Net Control expects each operator to form the habit of automatically recording for his own use and for the improved efficiency of the station, all possible indications and impressions of stations upon which bearings are taken. While this procedure should not reduce the number of bearings taken or the time devoted to covering the frequency assignment, it should enable the operators to collectively cover more ground and insure a more uniform performance. f. REPORTS OF BEAHIiv'GS. Bearings taken will be reported to Net Control in the manner prescribed by OPERATING INSTRUCTIONS, NUMBER 1, or subsequent modification thereto, but in addition to this, information as described in the foregoing paragraphs will be forwarded when it is thought to be of importance, such forwarding to be by CONFIr DENTIAL mail normally, but may be forwarded by dispatch if considered of sufficient importance. g. WATCH STANDING. General instructions of this type will not afford space for all details concerning the standing of watches at direction finder stations, so that only the more important points from an operation viewpoint will be included. The first and most important requirement is the continued maintenance of an alert and open mind on the part of the operator on watch. The taking of bearings brings into play all of thii finer senses of a radio operator, plus a complete understanding of the limitation of the direction finder, and an absolute requirement to think and act quickly. Some of the precautions which should be observed by direction finder operators are: Enclosure (A) to Com13 SECRET SERIAL #203035 Reproduced at the National Archives-Pacific Alaska Region (Seattle) GENERAL INS=CTIONS FOR STRATEGIC DIRECTION FII+DER STATION OPERATORS 2. Continued. WATCH STANDING. (Continued) g. (1) (a) KEEP ON THE ALERT. Use every available spare minute searching for new targets. Do not depend upon Net Control to always inform you when to take a bearing. Under wartime conditions a combatant vessel does little transmitting, and when necessity requires such a vessel to come on the air, transmissions are as brief as it is possible to make them. They do not make preliminary V's, nor give calls, but come up, send two or three short groups and are silent again. An overall time of 5 seconds on the air is not uncommon, and the direction finder operator must be alert and ready to take his bearing without waiting for instructions from Net Control. (b) LEAVE NOTHING TO CHANCE. Use pencil freely and record exactly your first impression of each bearing and do not change except by averaging. Do not refer to yesterdayts or any prior position of the same call. Do not allow the direction finder to remain on any one bearing for long periods of time. (c) FORGET ABOUT DEVIATION. There is little question but that deviation occurs in high frequency direction finder work, but the present state of accuracy, the lack of opportunities for exhausting research, and other factors make the use of any deviation dangerous. If research eventually uncovers any fixed rules of deviation, they will be applied at Net Control. Report the bearing taken exactly as you see it. (d) OBSERVE. ANALYZE, AIdD RECORD every bit of information attending each target on which a bearing is taken or attempted. Fill your "Remarks" column with collateral information such as other calls on the same circuit, addresses, and serial numbers in the heading of dispatches. You will find a great deal of useful information which assists in the identification of that particular station and associated stations. Such of this information as is considered of importance should be forwarded to Net Control as provided for in paragraph f. Enclosure (A) to Com13 SECRET SERIAL /203035 Reproduced at the National Archives-Pacific Alaska Region (Seattle) SECRET GENERAL INSTRUCTIONS FOR STRATEGIC DIRECTION FINDER STATION OPERATORS 2. Continued. g. WATCH STANDING. (Continued) KEEP DIRECTION FINDER AND OTHER EQUIPMENT IN GOOD CONDITION. At the beginning of every watch, the operator should take and record bearings on known fixed stations and check for accuracy. If no targets, as provided by the station assignment, are available, check bearings on known stations should be frequently logged for later analysis and as a check against possible error in the alignment of the direction finder. Any defective material noted by the direction finder operator should be reported immediately to the officer responsible for material upkeep. Ample spare parts should be kept on hand and available to the man on watch. i.L1IPdTAI:d ABSOLUTE SECURITY. Closely guard all classified correspondence, including these instructions, cipher devices, radio logs, reports, and everything pertaining to the operation of the station. DO NOT LEAVE STATION UNATTENDED FOR ANY REASON. Keep classified correspondence in safe when not in use. Treat as SECRET everything pertaining to the station's primary mission. Train yourself to make no mention of your work when outside of the direction finder house and give no one cause for suspicion by a "hush-hush" attitude. This applies to not only civilians but also to Naval personnel who are not engaged in direction finder work with you. Friends and acquaintances are often interested in you and your work, and either out of idle curiosity or with specific intent ask, "What do you do in the Navy?" Instead of saying, 9V work is secret, I can't talk about it", which would only incite more curiosity, endeavor to give an impression of normality and generality, such as, "Oh, Ifm just another radioman", or some other innocuous expression. Particularly in the case of an outlying station, adequate provisions should be made for the destruction of all classified correspondence, cipher devices, and data concerning the operation of the station in the event of capture by the enemy or abandonment of the station for any reason. Enclosure (A) to Com13 SECRET SERIAL #203035 Reproduced at the National Archives-Pacific Alaska Region (Seattle) GENERAL INSTaUCTIONS FOR STRATEGIC DIRECTION Fi:?DER STATION OPERATORS 2. Continued. g. l"IATCH STANDING. (Continued) THINK. The only possible way that an organization such as a direction finder Net may function successfully is to place entire dependence on the individual direction finder operator. Instructions must necessarily be brief, and often in dispatch form, especially under wartime conditions. The individual operators will be expected to be capable of copying foreign code at a high rate of speed and be trained to record exactly what has been transmitted. In most stationsj there will be no one with more experience than the operator to interpret the value of bearings and intercepts, and assist in sifting the valuable information from the routine or normal. Consequently, the obligation on the part of the direction finder operator to THINK and use sound judgment becomes much greater. (h) BE ACCURATE. Constantly endeavor to train yourself for increased accuracy. A copying speed of 18 words per minute with no errors is to be preferred to a speed of 20 words per minute with one error. In copying code groups, an error of one letter may completely change the answer when broken down. This especially applies to call signs--a single letter could easily indicate an entirely different type of vessel. h. TRAINING. (1) Under normal conditions, all direction finder radiomen should be trained in copying foreign codes as well as in the taking of bearings. Experience is the most desirable factor in the training of personnel for these purposes, and while all direction finder operators are given a preliminary course of instruction in this work, it has been definitely shown that the more experienced an operator is, the better he develops a "feel" or "sense" which helps him to take accurate bearings. Enclosure (A) to Com13 SECRET SERIAL #203035 Reproduced at the National Archives-Pacific Alaska Region (Seattle) -4W--W GENE'2j.L INST'ItiCT10NS F0:? S^t".ATECIC Dla'iC1^IOi'. FINDER STATIOi1 OPETA.'ORS 2. Continued. h. M9cINING (2) Under abnormal conditions, the demand for trained and experienced direction finder operators almost invariably exceeds the available supply, and necessity requires that personnel be assigned to this duty with a minimum of training. This, however, should be considered as a step towards further training by actual experience, under the guidance of Radiomen-in-Charge of direction finder stations. Enclosure (A) to Com13 SECRET SERIAL #203035 - 10 -