• An omnidirectional broadband antenna and 5 meter Rolatube mast system weighs 11 pounds and can be set up and ready for transmit and receive in less than six minutes by one person.
     An omnidirectional broadband antenna and 5 meter Rolatube mast system weighs 11 pounds and can be set up and ready for transmit and receive in less than six minutes by one person.
  • Near vertical incidence skywave enables high frequency systems to communicate in mountainous terrain.
     Near vertical incidence skywave enables high frequency systems to communicate in mountainous terrain.

Bringing Communications Back Down to Earth

June 1, 2018
By Kurt Stephens and Bill Whittington

High frequency radios can bridge a beyond-line-of-sight gap during operations in contested environments.

With the development and fielding of satellite communications throughout the U.S. military, today’s warfighters rarely use high frequency communications within and between units. International events have increased interest in high frequency communications as an alternative to connecting via satellites on current and future battlefields. U.S. military units already own a large amount of the radio equipment suitable for employment at various levels of the battlefield and for humanitarian relief as a redundant means of beyond-line-of-sight communications.

Prior to the advent of tactical satellite communications (SATCOM), high frequency (HF) radios were the prevalent communications method. Beyond-line-of-sight communications of voice or data has always been a challenge for fixed station, mobile and deployed warfighters as well as first responders. As SATCOM developed, however, it quickly became the preferred long-distance backbone of most voice and data transmissions. As the use of HF seriously declined, equipment was left on the shelf and training all but halted.

The advantages of satellite communications are well known, but the disadvantages are rarely noted. In any communications scenario, a redundant capability to transmit and receive messages beyond line of sight is a necessity for leaders who insist on covering all avenues for success. In addition, today’s warfighter is being challenged with satellite-denied environments.

Because HF has been relegated to a lower priority tier of training and deployment, the skills necessary for its successful use gradually have eroded. Understanding signal propagation and techniques of antenna employment have faded, as has the functional use of existing HF radios. Simultaneously, the cadre of experienced HF instructors has retired and hasn’t been replaced, resulting in a lack of genuinely experienced personnel with a strong background in the use of high frequency equipment throughout the armed services.

When environmental elements such as weather or terrain eliminate or degrade SATCOM as an option, warfighters must be well trained to use other methods of communication. Redundancy is still a key to success when requirements exceed the capabilities of a single method of communications. The capability to continue to communicate despite limitations provides an advantage over less prepared operational forces or governments.

The number of satellites available to handle communication requirements limits the use of SATCOM. During conflicts, military satellites are augmented by commercial satellites, which are more vulnerable to interference. In a contested environment, the demand for SATCOM often exceeds the supply, so an access priority system is established.

This is not the case for HF communications methods, which do not require prioritizing; only additional or an alternate set of frequencies or networks to facilitate communications are needed. Proper use of HF will alleviate the demands on SATCOM and supplement connections. However, good spectrum management is still needed.

Relying heavily on SATCOM also poses other challenges. The majority of today’s satellites are commercially owned, and all satellites are susceptible to jamming, eavesdropping, hijacking, antisatellite weapons, electromagnetic pulses, cyber or infrastructure attacks, and spoofing by either friend or foe. As a result, warfighters must be prepared to put an HF network into operation quickly as a redundant, or in some cases primary, communications method.

In addition to electronic warfare and cyber attacks, rugged terrain, foliage and unpredictable weather patterns can inhibit signals, causing them to be intermittent or even blocked. HF can overcome difficult terrain issues by configuring an antenna system that utilizes the technique of near vertical incidence skywave (NVIS) propagation. This technique is specifically used for close communications within a range of up to approximately 600 miles, particularly in mountainous or jungle terrain. NVIS typically uses frequencies between 2 megahertz and 10 megahertz (MHz). Although weather and the environment can increase local noise levels on HF to varying degrees depending on the areas of the spectrum used, today’s radios have better noise filtering and error correction than past equipment.

For the military, HF has often been considered difficult and less than reliable. Many tactical commanders do not want to deal with what they perceive as a static-ridden, signal-fading, multiple-interference and sunspot-affected frequency band. However, technical advances have corrected many of these issues. For example, automated link establishment is one of the most significant improvements because it enables the radio to find the best signal path between stations for existing and changing conditions automatically. Vocoder technology, among other improvements, can virtually eliminate background noise.

U.S. government and military organizations own a tremendous amount of spectrum that falls into the high frequency range of 2 MHz to 30 MHz. Consequently, the newest wideband technologies can provide larger slices of bandwidth that can be used by HF radios at a much higher level of data throughput than previously available. Limited fielding of this capability is underway.

Other technical advances in high frequency communications include embedded encryption, advanced algorithms, frequency hopping and wideband operation. In addition, recent developments in engineering comprising silicon carbide and gallium nitride integrated circuit materials can handle more power in smaller packages and are more compatible over a wider frequency range, and improved antennas enable connection at lower power ratings, saving critical battery life.

Other advances include radios that operate in low probability of intercept/low probability of detection modes at very low power settings and often below the noise floor. HF equipment can be easily cross-banded to other radio platforms with plug-and-play devices. This includes HF to SATCOM to very high frequency, ultrahigh frequency, Wi-Fi, cellphones, landline and even two-way handheld radios. This capability extends the range of line-of-sight radio equipment to hundreds or thousands of miles, including beyond line of sight.

Position reporting via HF has been used for many years. In addition, the equipment can be used to interact with international allies, local or regional friendly forces, and first responders who have little or no SATCOM capabilities.

Advances in military antenna designs have improved communications and are adaptable to any mode of radio equipment. Antennas that comply with size, weight and performance requirements are available with lightweight rollup masts for easy transport as well as rapid setup and recovery by warfighters.

The path forward for the military to enhance operations in a contested environment or to rebuild a redundant method of beyond-line-of-sight communications is to capitalize on existing resources and reintroduce HF radio and antenna employment training into a working level of knowledge for the operators.


WO-4 Kurt Stephens, USCG (Ret.), is the CEO and technical director for White Wolf Systems, and Lt. Col. Bill Whittington, USA (Ret.), is the senior marketing director for the company.

Enjoyed this article? SUBSCRIBE NOW to keep the content flowing.


Share Your Thoughts:

This article is a great testament to modern HF and the many applications it can be used with.

Thank you Dan, there has been a resurgence in HF spectrum usage as we've witnessed. I would love to see more written on the subject and how others are implementing with the different scenarios and mission requirements. Solutions are out there.

I suspect amateur radio operators could jump in as instructors, or even emergency operators via the MARS organization, as they’ve been operating HF communications continuously since the early 1900s.

Ken, well said, there is a lot of talent within the Amateur and MARS ranks that can contribute to bringing training up to speed.

Well Said!

Mention was made of the environment affecting HF radio and SATCOMs; however, no mention was made of what happens when the signals environment is taken out by nuclear weapons causing huge EMPs (electro-magnetic pulses) that will rapidly bugger-up transistors and the computers / equipment that they are in. The Russians were known to have developed work-rounds in the 1970s: how we sniggered when we found that, thanks to embargos, the Soviet Union could not develop decent transistors and modern communications devices but we laughed on the other side of our faces when we realised what their miniature valves could do and how robust they were against EMPs. I can only imagine how much their valve technology has advanced while ours has stagnated because no-one is looking at what happens if a war goes nuclear.


There is something worth to mention here... add also static electricity to the posible causes of major disruption of communications: During 1990, in operation Desert Storm, the modern Solid State equipment used by the Armed Forces was damaged due to strong desert sand storms. Static electricity built up on their antennas burning out the RF amplifiers on their radios. Collins KWM-2 transceivers (vacuum tube thermionic radios from the 60's-70's) were brought back into action in an urgent rush call to supply the need of communications for the Armed Forces. Thousands are still in use today by ham radio operators world wide.

As an overhauler of KWM-2s, perhaps I'm biased, but when up to spec these old soldiers are right up there with the SDRs and other modern tech radios.

High altitude EMP is going to remain a concern, and one can expect a number of potential adversaries to attempt to employ it in their favor. There are ongoing studies and research into EMP, its anticipated effects, and how to mitigate them. That said, and this is my distillation of the studies, we'll see some radios and other systems that are completely ruined, but others, that we once were sure would just fail, need a power-reset to restore. Keeping a spare set of gear might be a good idea, and in the warfighter community is certainly achievable, as a safeguard. It should be noted that we've really only seen one solar storm that caused widespread disruption in modern times, although solar events are listed as likely players in HEMP-type events. With that in mind, and with the number of X-class flares we've endured, while I'm always looking at new published HEMP research, I'm less frightened than I was. I suspect that a number of our FET-based designs will do better than we thought they might in the long run.

Great information, Kurt! The industry needed a reminder on the backbone of comms. Contact wishes you and Bill well.


Share Your Thoughts: