Better High Frequency Communications AUTHOR Major Michael G. Chlebik, USMC CSC 1990 SUBJECT AREA C4 EXECUTIVE SUMMARY TITLE: BETTER HIGH FREQUENCY COMMUNICATIONS THESIS: Through improved planning of high frequency spectrum usage, the MAGTF Commander can achieve better command and control through his use of high frequency communication links. ISSUE: Marine Corps units spend an inordinate amount of time trying to perfect high frequency (HF) communications in the field. Planning usually starts with a request to the Electromagnetic Compatibility Analysis Center (ECAC) for frequency predictions. As many items of information must be provided with the request, and not much information is available early in the planning cycle, the received answer is of little value. Frequency assignments are handed out next, after a poorly submitted unit request. The unit deploys to the field, and a Chirpsounder, if available, reflects a far different picture than the unit planned for. As a result, the unit cannot communicate. The Commander does not see communications serving command. Another tool is available: Prophet. It is a propagation prediction computer program that can assist the communicator in planning near-vertical incidence sky-wave (NVIS) transmissions needed for over-the-horizon (OTH) communications. CONCLUSIONS: Prophet has quick and accurate tools to get the Commander the answers he needs. It provides problem solving capabilities that evaluate his communications situation, and provides him with simple graphic products that give him real insight into problems of successfully communicating while avoiding enemy signal interception. The Chirpsounder transmitter is an easily isolated and identifiable target. The Commander must carefully consider sounder use on the battlefield. ECAC frequency predictions are available by message or letter request. The HF predictions provide only a ballpark figure. The predictions may not be received in a timely fashion to support the Commander in an age of maneuver warfare. RECOMMENDATIONS: The Marine Corps should teach Prophet in its University--let the HF planning mistakes be made on paper in the classroom, not during operations in the field. BETTER HIGH FREQUENCY COMMUNICATIONS OUTLINE THESIS STATEMENT. Through improved planning of high frequency spectrum usage, the MAGTF Commander can achieve better command and control through his use of high frequency communication links. I. High Frequency History A. Marine Corps Usage B. Fundamentals II. Tools of the Trade A. Chirpsounder B. Prophet C. Frequency Predictions III. Planning Example I A. Tactical Scenario B. Communications Mission Analysis C. Prophet Usage D. Sounder Usage IV. Planning Example II A. Tactical Scenario B. Communications Mission Analysis C. Prophet Usage D. Sounder Usage V. Comparison VI. Conclusion BETTER HIGH FREQUENCY COMMUNICATIONS Dear Ann: Why do I so often desire the best communications? And why do I so seldom get them?--Dilemma of a FMF Commander Dear Commander: Commanders should be counseled chiefly by persons of known talent, by those who have made the art of war their particular study, and whose knowledge is derived from experience, by those who are present at the scene of action, who see the enemy, who see the advantages that occasions offer, and who, like people embarked in the same ship, are sharers of the danger. If, therefore, anyone thinks himself qualified to give advice respecting the war which I am to conduct-- let him not refuse the assistance to the State, but let him come with me into Macedonia. He shall be furnished with a ship, a tent, even his traveling charges will be defrayed, but if he thinks this is too much trouble, and prefers the repose of a city life to the toils of war, let him not on land assume the office of a pilot. The city in itself furnishes abundance of topics for conversation. Let it confine its passion for talking to its own precincts and rest assured that we shall pay no attention to any councils but such as shall be framed within our camp.--Gen. Paulus (229?-160 B.C.) Rome 1 High Frequency (HF) radio continues to play a critical role in the communications architecture for the needs of the Marine Corps. The reliability of HF nets is governed by personnel training, equipment employed, outages directly related to changes and conditions of the ionosphere, and actions of enemy radioelectronic combat (REC) units. However, the standard HF communications techniques used in the past by the Marine Corps will not support the widely deployed over-the-horizon (OTH) amphibious assault. The standard HF communications techniques will not benefit the fast-moving formations of maneuver warfare ashore the Marine Corps expects to use to counter the modern threat. Linked closely with this are the problems that can be expected in deploying multichannel line-of-sight (LOS) systems with relays (retransmission sites) to keep up with fast-paced present and future operations. Thus high frequency radio and the near-vertical incidence sky-wave (NVIS) mode of propagation assume significant importance for the Marine Air-Ground Task Force (MAGTF) Commander. Besides improved communications, using mobile NVIS propagation also can result in several significant military advantages for the Commander, as noted by LTC Fiedler: . . .since all radiated energy returns to earth from above at approximately the same signal strength, direction finding on the signal becomes very difficult, and the probability of intercept and detection is greatly reduced, . . . because of the size, shape, and vertical direction of radiation, communications equipment can be hidden in depressions and under cover, thus making it harder to find. In fact, the criteria for selection of HF radio communications sites will have to be revised, because mobile NVIS will make possible the selection of much more survivable sites than those used today. . .studies by the [Army's] Armor Center have shown that often the first item detected on a vehicle with the engine off is the vertical radio antenna; a NVIS antenna can be made flat and is much harder to detect. . .horizontal mobile antennas do not have a spear-like construction, which in the past has caused injury and even death to U.S. troops.2 Through improved planning of HF spectrum usage, the MAGTF Commander can achieve better command and control through his use of HF communication links. His units will be harder to find by physical recognition or electronic signature. His communications will extend his "voice" on the battlefield in the exercise of command and control. He will have the electronic means to command and control, by using a minimum of key, well-understood phrases, and by talking directly to his key people. What is NVIS for a Commander? HF NVIS propagation is a process by which radio signals travel through the atmosphere from one antenna to another. Normally HF communications are accomplished by either ground-wave or sky-wave propagation. With current low-powered man-pack radios, ground-wave communications, the transmission of a radio signal along or near the surface of the earth, can be established and maintained out to 20-30 kilometers (km.). High powered equipment (mounted in jeeps or vans) can extend this range to 80-100 km. These limited ranges impact the Commander's ability to command and control those units assigned to him. The coverage from sky-wave communications, on the other hand, can vary from several kilometers to thousands of kilometers. Beyond the range covered by a ground-wave signal, sky- wave propagation is possible because of the bending of the radio signal by a region of the atmosphere called the ionosphere. The ionosphere is an electrically charged (ionized) region of the atmosphere that extends from about 60 km. to 1000 km. above the earth's surface. The ionization results from energy from the sun and causes radio signals to return to earth. The bending of a radio signal by the ionosphere depends on the frequency of the radio signal, the degree of ionization in the ionosphere, and the angle at which the radio signal strikes the ionosphere. Now, Commander, this is what you need to do. You have already realized that to command and control your units, you must have reliable communications with them. It's your communicator's job to establish and maintain communications for your unit. After all, the primary purpose of communications is to serve the command. The Commandant of the Marine Corps says: Technology can enhance the ways and means of war by improving man's ability to wage it, but technology cannot and should not attempt to eliminate man from the process of war. Better equipment is not the cure for all ills; doctrinal and tactical solutions to combat deficiencies must also be sought. 3 Commander, you must become more involved. The doctrinal and tactical solutions to communications deficiencies must be found. The locations of the communications sites will be very important in determining the success of your communications. The best positions within range for your communications sites must be found. You have been assigned certain communications equipments within your unit's Table of Equipment (T/E). The best equipments to use for a particular situation must be determined. The power, antenna and modulation type for each transmitter must be determined. The antenna for each receiver must be found out. You have been allocated a set of frequencies by higher headquarters. From these frequencies you must select the best ones for the priorities of communications that you have established. Also, Commander, this is what you need to watch. You need to account for physical factors that affect communications. HF communications are affected by many factors, such as distance, time of day, season, latitude and solar storms. Understanding the importance of these conditions will help you command and control ("make the links work") in the face of adverse conditions. You need to assess the vulnerability of your signals to hostile forces. If the enemy can intercept your signals, they can monitor your transmissions, figure out your location or disrupt your communications by jamming. Perhaps you have allowed for the submission of an essential element of information (EEI) early in the Command and Staff Action Planning Sequence: Determine the capability of the opposing force to conduct electronic warfare operations in the MAGTF Area of Influence. If so, with what sized units and locations, and with what capability (meaconing, intrusion, jamming, and/or interference). Special attention to radioelectronic combat units operating vicinity grid square AB12345678. An EEl is information on enemy, terrain, or weather essential to you to do your mission. You begin to focus on the enemy and his ability to target your command, control and communications facilities. You think where MAGTF command and control weaknesses lie, and you protect your weaknesses. Command, control and communications (C3) countermeasures (C3CM) is defined as the integrated use of physical destruction, electronic warfare, operations security and military deception, all supported by intelligence, with a two-fold intent--degradation of enemy C3, and protection of friendly C3 from enemy degradation. Because a weapons system is much more than a piece of hardware within the context of C3CM, an expanded definition of weapons system is provided. The major components are the weapon itself, at least one sensor associated with that hardware, and a command and control subsystem with its supporting communications to link the sensor information with the weapon itself, and to control the weapon's actual functioning. According to Littlebury: The essence of C3CM is attacking the enemy's weapons system in terms of its associated sensors and command and control (counter C3), rather than the traditional concept of attacking the weapon itself. Conversely, protecting friendly C3 involves hardening our own weapon system sensors and command and control against enemy degradation. 4 Commander, there are many advantages in using the NVIS concept. There is a lower probability of geolocation. NVIS energy is received from the sky at very steep angles, which make direction finding from nearby (but beyond ground-wave range) locations more difficult. Communications are harder to jam. Ground-wave jammers are subject to signal loss along the path to your receiver. Terrain features can be used to mitigate a ground-wave jammer without degrading the desired friendly communications path. The jamming signal will be reduced by terrain while the sky-wave NVIS path loss will be constant. This will force the jammer to move very close to the target receiver or put out more power. Either tactic makes jamming more difficult. Friendly operators can use low-power successfully. The NVIS mode can be used successfully with low-power HF radios. Commander, you begin to practice C3CM as it relates to your command post's electronic signature. When communications outages occur, it is first necessary to recognize that one has occurred, and then take actions necessary to pass time sensitive (high precedence) information by any means available. The tactical commander must be provided the information he needs to fight and win. Restoration actions may include supporting propagation over the High Frequency path desired by changing the transmitting frequency. The AN/TRQ-35(V) Chirpsounder can meet this latter need by displaying those frequencies which are presently propagating, and by displaying a summary of the amount of time each channel has been used in either the last 5 or the last 30 minutes, whichever is desired. The employment of the sounder system enables the operator to observe a display of those frequencies which are actually propagating and the mode(s) by which the propagation is accomplished. The spectrum monitor allows the operator to determine which frequencies are being used and how busy they are. If it is determined that communications are possible but are not gotten, an operator or equipment problem is probably occurring. The Chirpsounder has a transmitter, three receivers, and a spectrum monitor. The transmitter and receiver are located on opposite ends of the path being sounded. The transmitter may be collocated with other communications equipment or may be completely detached so long as it has the required power source. Since its transmissions have a distinct electronic signature and the radiated output has a long "transmit on" time duration, the Chirpsounder transmitter is an easily isolated and identifiable target. After the receiver is established with power and an antenna, time synchronization to the transmitter and initial programming must be accomplished. Collocation of the sounder receiver and spectrum monitor provides the operator with the necessary information to enable selection of the optimum frequencies from the viewpoint of received signal strength and unused or minimally used frequencies. Note that the U.S. Military Communications-Electronics Board (USMCEB) has established a worldwide Chirpsounder Directory in support of communications operations and planning to promote common sounder transmitter use where feasible. An AUTODIN Address Indicator Group (AIG) has been established to distribute the initial directory and subsequent changes. Your communicator can request this information for planning purposes. Commander, what can the Chirpsounder do for you? The AN/TRQ-35(V) sounder system excels in a real-time, point-to- point, noncovert environment. It also excels during periods of abnormal propagation which are not modeled in a computer- based predictive system. Employment of a chirpsounder is mission oriented; only a sounder can deal with a post nuclear environment. A predictive system lends itself to the predictive and communication planning environment, and is more flexible in assessing multiple circuits over a large are, and can consider communication planning in a hostile electronic warfare environment. One such system is Prophet. The Advanced Prophet System is a propagation prediction computer program which is designed to provide rapid user- interactive predictions for circuits between any two points on the earth's surface. The basic parameters are maintained in a user-controllable scenario, which may be manipulated. Sites are defined by name, latitude, longitude, antenna, antenna bearing, transmit power, network, and speed. If moving, destination latitude and longitude, and departure date and time definitions are needed. Hostile sites are members of an opposite network. A special module is used to create only those antenna patterns desired by the user. Skywave propagation characteristics are computed for a single transmitter to receiver path, obtaining maximum usable frequency (MUF), frequency of optimum traffic (FOT), and lowest usable frequency (LUF) information. Site latitude/longitude, date, time, frequency, and 10 cm. flux or sunspot number (current sky conditions) are required inputs. Some products also compute field strength or signal-to-noise (S/N) values. This is where proper antenna definitions and orientation are important. Other factors, based on modulation type selected (e.g. voice, FAX), are bandwidth and required signal-to-noise ratio for successful communications. Ground-wave propagation is computed from antenna heights, polarization, terrain type (or ground conductivity and dielectric constant), and if land, surface cover, or if sea-water, wind velocity, for surface roughness. Noise, for both ground-wave and sky-wave propagation, is computed based on a user-selected man-made noise type, and if enabled, atmospheric noise. All computer modules use different combinations of the above computations, and either process a single transmitter to receiver path or multiple paths to generate a display output. Some products also will use a hostile site designation, which is explained in detail in the on-line help function for those products. The Advanced Prophet system is designed to be largely self-tutorial by use of an on-line help command. There are restrictions on use of Prophet, according to the Navy: The Advanced Prophet system contains information and capability subject to the International Traffic in Arms Regulation (ITAR) or the Export Administration Regulation (EAR) of 1979 which may not be exported, released, or disclosed to any foreign nationals inside or outside the United States without express permission from Chief of Naval Operations under any circumstances. 5 Commander, what can Prophet do for you? Your communicator uses Prophet because it help him make important recommendations in setting up and operating communications links. Prophet has quick and accurate tools to get you the answers you need. It provides problem solving capabilities that evaluate your communications situation, and provides you with simple graphic products that give you real insight into problems of successfully communicating while avoiding enemy signal interception. The HF sky-wave predictions produced by the Electromagnetic Compatibility Analysis Center (ECAC) and other Department of Defense activities are based on computer programs developed by the National Telecommunication Information Agency (NTIA) in Boulder, Colorado, and modified by the individual agencies. These predictions are averaged over a 30-day period and as such provide only a ballpark figure. On any given day, the actual optimum frequencies may be considerably above or below predicted values, particularly during periods of high solar activity. ECAC's propagation predictions are provided primarily by AUTODIN or letter to the Marine Corps. The following information must be provided to ECAC for propagation predictions: 1. Propagation mode (sky-wave or ground-wave) 2. Day, month, year of start, and end of transmission 3. Transmitter site name 4. Receiver site name 5. Transmitter and receiver site coordinates [format varies] 6. Emission type (6K00B9W, etc.) 7. Transmitter power in watts 8. Type of earth at each antenna (sea water, desert, marsh, average soil, etc.) 9. Type of man-made noise area (rural, suburban, urban or industrial) 10. Antenna type (whip, doublet, AS-2259, etc.) 11. Antenna height and/or length, in feet or meters. 6 Commander, what can frequency predictions from ECAC do for you? Your communicator knows that varying degrees of operational support are available from ECAC, ranging from propagation prediction support to complete and total exercise or contingency communications engineering for areas throughout the world, including: l. More comprehensive propagation analysis (e.g. calculation of S/Ns, signal level contours, sky-wave or ground-wave comparisons, etc.) 2. Listing of frequencies currently in use for any area of interest. 3. Antenna radiation patterns for most commonly used types of antennas. 4. Frequency assignment and circuit routing recommendations (based on propagation and considerations). 5. Determination of antenna locations for best coverage of beaches, object areas, or avenues of approach, or for best shielding from unwanted intercept. 6. Determination of the most reliable means of communication between two points. 7. Radar coverage charts. 8. Terrain path profiles. 7 Commander, do you have time to make a request to ECAC for support in your modern warfare environment? Do you have the tools available for your communicator to plan communications for you, now? It is time to apply the HF communication tools discussed above to a tactical scenario. Perhaps an Initiating Directive has established Operation MOSSBACK, and provided the following mission to an Amphibious Task Force (ATF) comprised of Naval and Marine Corps forces: Conduct an amphibious assault on Jutland, in coordination with a counter-offensive by SACEUR [Supreme Allied Commander, Europe], for the purpose of establishing a beachhead to permit the landing of follow-on forces, in order to threaten the northern flank of Warsaw Pact. 8 As an early phase to this scenario, Marine Corps aviation elements deploy from Continental United States (CONUS) to advance bases in England in order to commence preassault operations. The 2d Marine Aircraft Wing (MAW) Command Element (CE) is at Elvington, United Kingdom (UK.). Commander Landing Force (CLF) plans to establish his command post (CP) vicinity Esbjerg, Denmark when he goes ashore. He requires communications with his Aviation Combat Element (ACE), 2d MAW. The communications mission analysis reveals that satellite or HF communications are the most probable, as the commercial telephone system in Denmark has been rendered inoperable by the enemy. Although satellite connectivity will be pursued by the communicator, channel availability aboard the satellite may preclude access for the ACE at this time. An attached satellite communications team may not be familiar with their equipment to allow for its use. Thus the initial communications requirement is to determine the range of frequencies suitable for HF communications between the CLF and ACE in order to request frequencies that will propagate. The CLF's Planning Guidance stated that HF communications were to be ascertained for 0600 Universal Time (UT) on 30 April, 1990, for planning. Now, the communicator must answer the following: 1. If communications is required at 0600 UT, what is the highest frequency that can be used? What is the lowest frequency that can be used? 2. If a frequency of 8.0 Megahertz (Mhz) is the only available frequency assigned for use, what time of the day are communications possible? A request for ECAC assistance is possible in this scenario. Initially the ECAC HF Predictions Manual- Supplement is researched to see if propagation planning has been previously published by ECAC. Then a request is made to ECAC for frequency predictions. As many items of information must be provided with the request, and not much information is available early in the planning cycle, the received answer is of little value. Frequency assignments are handed out, after a poorly submitted unit request. Prophet usage is possible in this scenario. Recall it is a propagation prediction computer program that can help the communicator in planning near-vertical incidence sky- wave (NVIS) transmissions needed for over-the-horizon (OTH) communications. Figure 1 reflects the output of a Diurnal plot. Observe that at 0600 UT, the highest frequency that can be used is 9.7 Mhz, and the lowest frequency that can be used is 2.8 Mhz. Figure 2 shows the result of a Raytrace plot. Scrutinize that a single hop path exists around 50 degrees--an NVIS antenna should be used (dipole or equivalent). Figure 3 displays the product of a Field Strength plot. Study that communications are only possible between 0400-0900 UT and 1600-1900 UT, because the signal- to-noise content is greater than 10 during those times only. Chirpsounder usage is possible in this scenario. Previously established sounder transmitter locations in the United Kingdom have been noted by the communicator. He recognizes that the path from an actual sounder transmitter site to Denmark is nearly identical with the path between the ACE and CLF locations (Elvington, UK and Esbjerg, Denmark, respectively). The CLF's communications element takes a receiver and spectrum monitor ashore at Esbjerg; as these are passive devices, no frequency clearance is necessary. The Chirpsounder reflects a far different picture than the unit planned for. As a result, the unit cannot communicate. The Commander does not see communications serving command. Let's modify the present scenario by including elements from the G2's response to the EEI previously stated. Recall the Commander asked the Intelligence community to determine the capability of the opposing force to conduct electronic warfare operations in the MAGTF Area of Influence. The response back indicated enemy intercept sites at Esbjerg, Hirtshal, Klitgard, and Logstor, Denmark. The response also stated an enemy jamming site at Moscow. Recall the CLF's Planning Guidance stated that HF communications were to be ascertained for 0600 UT on 30 April, 1990, for planning. Now, with a threat network established, the communicator must answer the same questions: 1. If communications is required at 0600 UT, what is the highest frequency that can be used? What is the lowest frequency that can be used? 2. If a frequency of 8.0 Mhz is the only available frequency assigned for use, what time of the day are communications possible? A request for ECAC assistance is not possible in this scenario. The tempo of operations precludes receiving a response to arrive in time to act upon it. Prophet usage is possible in this scenario. Figure 4 reveals the output of an Area plot. Inquire that at 0600 UT, the communications ranges of both stations extend for long distances. Earlier noted was that the stations may not be in communications with each other at 0600 UT. Figure 5 introduces the output of a Secure plot. Gaze that at 0600 UT, the highest frequency that can be used is 9.0 Mhz, and the lowest frequency that can be used is 8.0 Mhz. There are no periods where the CLF's communications do not propagate to intercept sites. The lightly hashed areas viewed represent no direction finding is possible, although enemy intercept is possible. For a frequency assignment of 8 Mhz, no intercept-free communications are possible. Chirpsounder usage is not possible in this scenario. Although previously established sounder transmitter locations in the United Kingdom were noted by the communicator, he recognizes that the path from an actual sounder transmitter site to this potential sounder receiver site in Denmark is not what is needed. He cannot afford to put a sounder transmitter at CLF's Command Post or with the distant station, as the transmitter has a distinct electronic signature and the radiated output has a long "transmit on" time duration. As the Chirpsounder transmitter is an easily isolated and identifiable target, its use at CLF's Command Post or at the distant station could subject those units to enemy C3 targeting. Although CLF's communications element took a receiver and spectrum monitor ashore at Esbjerg, they will not help him here. Commander, the first scenario is the kind of problem you experience in peacetime: point-to-point HF communications. Typically there are too many excuses given when the communications mission fails, rather than achieving mission accomplishment. The reliability of HF nets is governed by personnel training, equipment employed, outages related to the ionosphere, and actions of enemy REC units. In this planning example, you controlled the first two. The second scenario is like those uncovered on deployments or war--the threat is real. Actions of enemy REC units are not controlled by you. If you do not train in peacetime for their actions, what will you do in war? Commander, you can have successful HF communications. The reliability of HF nets is governed by personnel training, equipment employed, outages related to the ionosphere, and actions of enemy radioelectronic combat (REC) units. Through improved planning of high frequency spectrum usage, the MAGTF Commander can achieve better command and control through his use of high frequency communication links. Commander, you control the training. Prophet has quick and accurate tools to get you the answers you need. It provides problem solving capabilities that evaluate your communications situation, and provides you with simple graphic products that give you real insight into problems of successfully communicating while avoiding enemy signal interception. The Chirpsounder transmitter is an easily isolated and identifiable target. You must carefully consider sounder use on the battlefield. ECAC frequency predictions are available by message or letter request. The HF predictions provide only a ballpark figure. The predictions may not be received in a timely fashion to support you in an age of maneuver warfare. Commander--teach Prophet. Let the HF planning mistakes be made on paper in the classroom, not during operations in the field. Click here to view image FOOTNOTES 1Come With Me To Macedonia or Life in the American Civil Service, p. 1. 2David M. Fiedler, LTC, ARNG, "Mobile NVIS: The New Jersey Army National Guard Approach," Arms Communicator, Vol. 12 (Fall, 1987), p. 10. 3A. M. Gray, Gen, USMC, Warfighting, (United States Department of Defense, Headquarters, U.S. Marine Corps, FMFM 1, 1989), p. 53. 4F. E. Littlebury and D. K. Praeger, Invisible Combat: C3CM A Guide For The Tactical Commander, (Armed Forces Communications-Electronics Association International Press, Washington, D.C., 1986), p. xii. 5Warning contained on Advanced Prophet Version 3.2 Executive Diskette, (United States Department of Defense, Naval Ocean Systems Center, San Diego, CA., Dec., 1987). 6James L. Small, HF Predictions Manual, (United States Department of Defense, Electromagnetic Compatibility Analysis Center, Annapolis, MD., ECAC-CR-82-125, Nov., 1982), p. 5/26. 7Small, p. 5-27. 8D. K. Roeber, Cmdr, USN, Amphibious Operations-- Operation MOSSBACK, (United States Department of Defense, Marine Corps University, Quantico, VA., C(C)2600, 1990), p. AS/C/3. BIBLIOGRAPHY 1. Chlebik, M. G., Maj, USMC, The Prophet Primer, (United States Department of Defense, Dec., 1986), pp. 1-172. 2. Come With Me To Macedonia or Life in the American Civil Service, pp. 1-344. 3. Fiedler, David M., LTC, ARNG, "Mobile NVIS: The New Jersey Army National Guard Approach," Arms Communicator, Vol. 12 (Fall, 1987), pp. 6-10. 4. "Field Power Requirements For Micro Computers," CG I MEF Naval message 130216Z Feb 1986. 5. Gray, A. M., Gen, USMC, Warfighting, (United States Department of Defense, Headquarters, U.S. Marine Corps, FMFM 1, 1989), pp. 1-88. 6. LaBahn, R. W., Operational Users Manual for Advanced Prophet on MS-DOS-Based Microcomputer Systems, (United States Department of Defense, Naval Ocean Systems Center, San Diego, CA., Technical Document 848, Aug., 1985), pp. 1-54. 7. Littlebury, F. E. and Praeger, D. K., Invisible Combat: C3CM A Guide For The Tactical Commander, (AFCEA International Press, Washington, D.C., 1986), pp. 1-81. 8. "Operators Manual for the United States Coast Guard Advanced Prophet System," (United States Department of Defense, Naval Ocean Systems Center, San Diego, CA., Nov., 1987), pp. 1-278. 9. "Pacaf Ind Daily Intelligence Summary (PACAF DISUM 093- 86," PACOPS HICKAM AFB HI message 032300Z Apr 1986. 10. Pocock, Emil, "Propagation Forecasting During Solar Cycle 22," QST, Jun., 1989, pp. 18-20. 11. Raub, S. A., Capt, USMC, "Command, Control, and Communications Countermeasures," Marine Corps Gazette, Jun., 1984, pp. 56-62. 12. Rino, C. L., "Radiowave Propagation Disturbances," Journal of Electronic Defense, May, 1984, pp. 53-58, 13. Roeber, D. K., Cmdr, USN, Amphibious Operations-- Operation MOSSBACK, (United States Department of Defense, Marine Corps University, Quantico, VA., C(C)2600, Feb., 1990), pp. 1-AS/H/2. 14. Rosenthal, D. A., "Geophysical Alert Broadcast User's Guide," (United States Department of Defense, Naval Weapons Center, China Lake, CA., NWC TP 6981, Mar., 1990), pp. 1-20. 15. Rose, R. B., Advanced Prophet HF Assessment System, (United States Department of Defense, Naval Ocean Systems Center, San Diego, CA., Jan., 1984), pp. 1-108. 16. Rose, Robert B., "MINIMUF: A Simplified MUF-Prediction Program for Microcomputers," QST, Dec., 1982, pp. 36- 38. 17. Sawyer, Kathy, "Solar Tantrum Erupting," The Washington Post, Dec. 18, 1989, p. A3. 18. Shuch, H. Paul, "Gaining on the Decibel," QST, Mar., 1986, pp. 28-31. 19. Small, James L., HF Predictions Manual, (United States Department of Defense, Electromagnetic Compatibility Analysis Center, Annapolis, MD., ECAC-CR-82-125, Nov., 1982), pp. 1/1-B/22. 20. "Tactical Single-Channel Radio Communications Techniques," (United States Department of Defense, Department of the Army FM 24-18, Dec., 1984), pp. 1/1- N/10. 21. Walters, Roland B., Capt, USMC, "Our Continuing Self- Delusion Regarding Tactical Intelligence Capabilities," Marine Corps Gazette, Mar., 1990, pp. 56-58.
