An HF “Renaissance”: Militaries reinvests in shortwave communications

Many thanks to SWLing Post contributors Michael Guerin and Dennis Dura who share the following story from C4ISR.net (my comments follow excerpt):

LONDON — Special operations commands across Europe are ramping up their capabilities with high-frequency communications to ensure connectivity on the battlefield. Leaders there are turning to high frequency communications as a way to optimize properties that provide a low probability of interception and detection.

Special forces in France, Germany, Poland and Ukraine continue to receive high-frequency, or HF, systems as a way to diversify communications plans, industry sources confirmed to C4ISRNET.

Some special operations organizations have selected L3Harris’ AN/PRC-160(V), industry sources said.

Enhancements in HF come at a time when NATO members and partner forces are suffering from a disruption of satellite communications, particularly along the alliance’s eastern flank where Russian armed forces continue to conduct electronic warfare.

In an online presentation to the Association of Old Crows on Aug. 6, Paul Denisowski, product management engineer at Rohde and Schwarz North America, described how communications satellites are vulnerable to antisatellite systems as well as ground-, air- and space-based “kill vehicles.”

“China, Russia and the U.S. have all carried out ASAT tests and many other countries are developing ASAT capabilities,” Denisowski said, using an acronym for anti-satellite. To boost resilience, some commands are turning to high-frequency communications.

During the presentations “Lost Art of HF” and the “Rebirth of Shortwave in a Digital World,” Denisowski explained that HF is making a comeback in local and global communications. This renaissance comes as the result of improvements in a range of fields, including antenna design, digital modulation schemes and improved understanding of propagation.

The market is also helped by reductions in size, weight and power requirements as well as the introduction of wideband data, enhanced encryption algorithms and interoperability with legacy HF sets, he said.

“This means end users are now benefiting from easier-to-use and cheaper solutions featuring improved data performance, audio quality, availability and operation. And because of a lack of infrastructure, HF is less expensive and relatively robust, although solar events may temporarily disrupt HF communications,” he said. Specific upgrades include “Adaptive HF,” which comprises automatic selection of frequency and the establishment of communication through automatic link establishment, or ALE, technology.

The latest technology of its type — 4G ALE — is capable of supporting wideband HF communications, or WBHF for short, providing end users with the ability to “negotiate bandwidth, modulation type, error correction and the number of sub-carriers,” Denisowski explained.

“ALE selects frequencies using link quality analysis, which allows it to listen and determine if a channel is in use and adapt if conditions change,” he said.

He added that HF can now support data rates up to 240 kilobytes per second on a 48-kilohertz channel, particularly useful for more robust communications in hostile environments.

“WBHF has already [been] used in military trials. It’s a technology which is most definitely here and now,” Denisowski said.

[…]The report explained how the U.S. Army and European NATO partners explored such scenarios during a series of joint exercises in 2019 and 2020. “A new need arrives for alternative communication skills, justified through the increasing vulnerability from SATCOM jamming as well as the potential failure of SATCOM as a result of attacks on spacecraft or through the use of anti-satellite surface-to-air missiles,” the report’s author, Jan Pätzold, told C4ISRNET. “The development of alternative skills is important to reduce dependence on SATCOM.”

According to Pätzold, so-called Skywave HF, which bounces signals off the ionosphere, enables beyond line-of-sight communications across “thousands of kilometers” without requirements. HF communications is also ideally suited to supporting local network coverage. “This offers advantages over SATCOM in urban areas, but also in mountainous areas or far north latitudes where no line of sight to existing satellites is possible,” Pätzold said

Click here to read the full story at C4ISR.net.


My comment: What’s old is new again

As I’ve said in previous posts:

The shortwaves–which is to say, the high-frequency portion of the radio spectrum–will never disappear, even though international broadcasters may eventually fade into history. I often think of the shortwave spectrum as a global resource that will always be here, even if we humans are not. But on a brighter note, I expect the shortwave spectrum will be used for centuries to come, as we implement various technologies that find ways to make use of the medium.

HF communications require so little infrastructure to be effective. It’s a global communications medium that carries messages and data at the speed of light with no regard for national borders. Sure, there are reliability issues with HF propagation, but even amateur radio enthusiasts employ weak-signal digital modes that almost seem to defy propagation. I’m certain with the backing of the military, even more robust digital modes will be used (above and beyond ALE).

Even the business world sees opportunity. Case in point: we’ve seen stock traders set up point-to-point HF communications to edge out their competitors who rely on fiber optics.

HF systems are more durable and easier to harden to endure times of intense space weather events that affect our sat networks as well.

But then again, I’m preaching to the choir.

Spread the radio love

20 thoughts on “An HF “Renaissance”: Militaries reinvests in shortwave communications

  1. Mike Bennett

    ..as this articles states…”Skywave HF bounces off the ionosphere to go thousands kilometres”! …but the article doesn’t state if this probagation is good for daytime/nighttime/all weather transmission! And if so, then this would solve the AM/MW & RFI transmission problems and it would be the holy grail instead of DRM, IBOC, etc.! ….? What to think?

    Reply
    1. Mangosman

      Mike,
      The ionosphere, the radio mirror in the sky overcomes the effect of terrain, the horizon, thick forest etc which blocks transmissions in the VHF, UHF and SHF bands used by mobile phones, FM radio and television. Most of these transmissions are limited to about 100 km for a high powered transmitter using a high tower on the top of a hill.

      The Ionosphere varies depending on space weather https://www.sws.bom.gov.au/Space_Weather
      This is why most broadcasters change the transmission frequency at sun rise and sunset.

      The other issue with using the ionosphere is the receiver may get multiple reflections from different parts of the sky. This makes different path lengths and signal delays. This causes phase and fading effects in analog. In digital transmissions such as DRM the data is sent in bursts and only the beginning of each burst is used by the receiver, so only the shortest delayed signal is used The longer paths are ignored.

      Digital transmissions are sent in a pseudo random order which when combined with error correction allows the receiver to correct the errors caused by lightning strikes and interference.

      Digital transmission produces a clear noise free reception and in a broadcasters’ terms can also carry stereo sound which sounds great. When the errors are excessive the output is muted. This usually occurs when the AM equivalent is almost unintelligible.

      IBOC or its trade name HD Radio uses the adjacent channels used by other broadcasters. The standard does not cover high frequency broadcasting. Other countries would not want this interference. DRM is the only digital broadcasting standard which is accepted for high frequency broadcasts, along with all other broadcasting bands.

      Reply
  2. Mark

    Just what we need, more QRM on the ham bands.

    The 40 M Ham band here in Europe is regularly plagued with QRM from I think it is OTH Radar, why bother the tiny 40 M band we have in Europe ? No doubt the situation will get worse now.

    Reply
  3. Mark

    No doubt we’ll see more QRM on the ham bands.

    I don’t know why the military have to use the Ham bands for their OTH Radar or whatever that QRm does be around 40 meters loudest in Europe no doubt the Russians….. But it can wipe out half the 40 meter band…..

    Reply
  4. Arthur Ascii

    I was wondering how long it would be before someone had to get DRM etc
    into the conversation.

    It didn’t take long 🙂

    Reply
  5. Des Walsh

    Not only are satellite systems vulnerable but also are internet cables on the sea beds – snip, snip , snip ! Des Walsh EI5CD

    Reply
    1. Tim N4TCM

      I think the broadcasters need to come back. Internet feeds just dont sound the same. The apps always have low levels. Cant hear them half the time. Radio Australia an old favorite. Sounds terrible on the TuneIn app. Domestic AM/FM sound great.

      Reply
      1. F9h

        When the fit hits the shan and the govt. shuts down the internet, we’ll be SOL without broadcasters, so I hope you’re right.

        Reply
        1. Laurence N.

          If a government actually did that, what good do you expect the broadcasters to provide? If your plan sounds like “People tune into the international broadcasters, learn about the abuses of the local government, get angry, and overthrow the dictatorship”, you don’t need the first two steps as you could replace the plan with “People like the internet and are unhappy that it’s no longer available, get angry, and overthrow the dictatorship”. Either way, their chances of succeeding are unchanged.

          Reply
  6. Wesley Griffin

    When Desert Shield got rolling some military units (core of engineers) were using trucker radios (CBs)
    The military had lots of communication failures in Desert Storm, don’t know the exact reasons but i have been told their HF radios worked great but were overloaded with traffic.

    Reply
  7. Kire

    To me at least, the HF frequencies would be prime for military and intelligence communications because as the article states, digital modes and encription technology have improved so much.
    Since the mass public has been moved over to internet communications (which are easily monitored, and can be blocked), it leaves the shortwaves much more available, yet less open to penetration with modern encription techniques applied.

    Reply
    1. Mangosman

      The advantage of cable communications these days is that it is fibre optics. When means to monitor traffic, you have to break the glass and weld it to another fibre optic cable to a photo transistor receiver. The sender can detect the break and stop transmission. The other end will also not get the messages.

      My description of digital transmission techniques did not touch on the use of encryption. Not only can you transfer characters to different characters using a ‘seed’ pattern there are additional options.
      The way parity error correction algorithms are calculated can be changed regularly. When the data is stored prior to transmission, the order that the data is read during transmission can be controlled by an encryption algorithm giving even more protection.

      The characteristic of HF transmission and satellite transmissions is that the enemy can also receive the signal along with your own troops. This is why encryption and the above techniques need to be used, with frequent changes in the encryption patterns so that by the time the patterns are ‘cracked’ a new one is being used. Cables need less encryption because the path has to be broken to detect the transmission.

      Reply
      1. KiwiSDR

        “Which means to monitor traffic, you have to break the glass and weld it to another fibre optic cable to a photo transistor receiver.”

        Uh, no. Sincerely, the US NSA (and their counterparts worldwide).

        Reply
        1. Laurence N.

          Both of you are correct. Tapping a cable in the middle is hard to do without tipping off the people on either end, but don’t forget that data going through a cable is also going to go through several boxes on either end. Someone with access to those can tap the signal without alerting the sender. Encryption for sensitive messages sent over cable is important unless you either a) control everywhere the cable goes or b) use a cable which can’t easily be watched without damaging it and you control everywhere the encoders and decoders are. The reason that it is of less concern to the typical public is that our communications over cables aren’t of much interest to most people, and therefore there’s little benefit investing in the tech to intercept them. The same is not true for military information, so they’ll be using encryption as much as possible.

          Reply
  8. Dirk Rijmenants

    No rebirth, as HF never left the military. The network and the satellite bubbles burst quickly. Both will be totally unreliable and most likely not even available in times of serious conflict. But also the evolution of pimping HF and transporting ever more information is a risky path, as a higher bit rates is inversely proportional to reliability. Same with Morse, abandoned a few years ago, but quickly returned after they realized that only Morse would do the job in the worst conditions. Morse courses are reintroduced everywhere.

    We see it with a lot of equipment, the more digital and high-tech we go, the more likely your link is either working well or working not at all. In contrast, the old “analogue” gear is often still usable and readable on a very weak and distorted link, and we can mostly still tweak it a bit. If the going gets tough, we hear more cursing today than in the old days. The choice then is, when SHTF, would a commander prefer high-tech digital gear, and in the end not receive that fancy digital map, or use simple and sturdy gear and be sure they receive that report in words and figures.

    Meanwhile, even fighter pilots’ penny dropped, and now train on flying without GPS.

    Reply
    1. Mangosman

      It is tempting to say that the old analog ways are best, because they are familiar.
      Carrier Wave Morse is the most likely to get through because it is a digital transmission system of a very low bandwidth. The low bandwidth means that the receiver can use a very narrow filter to remove much more noise.
      Then came Piccolo for Defence which was like Morse code but used multiple (audible) frequencies to increase the bit rate. It was the forerunner to digital transmission systems.

      Now, because of microprocessors and memory along with the Fast Fourier Transform mathematics, the Australian COFDM modulation system was born. Its chief advantages are that a number of digital signals are mathematically combined to produce hundreds or thousands of individual carriers which are on or off. Like the Piccolo system above, but on steroids. In addition mathematics is also applied to add signal related and calculated parity data which is used at the receiver end to detect faulty data. It is done in such a way that many errors can be corrected. The data to be sent is stored in memory and sent out in a pseudo-random order. If the memory is long enough there is enough good data to allow errors caused by impulse noise to be corrected. Typical sources of impulse noise is lightning and other arcing sources. Since much HF transmissions are reflected from the ionosphere, it is common to get multiple reflections of different path lengths. This causes fading in analog. Digital transmissions are sent in bursts and the receiver will only process the first part of each burst, so that the later reflections are ignored.
      The end result is that a transmission system can be set to be very robust but have a low bit rate and under better conditions it can be set for a much higher bit rate which doesn’t need as much protection.

      There was a side by side comparison of AM and Digital Radio Mondiale in the MF band in South Africa. The transmitter power was slowly reduced and the receiver outputs were recorded. The DRM audio only broke up after the AM was totally unreadable.

      I used a portable DAB+ and FM receiver in an area of low signal strength. The transmitter power of the FM and the DAB+ signals were identical and on the same tower. The FM and DAB+ dropped out simultaneously.

      Reply

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