The Past is Present in Wireless Technology

It’s easy to think of wireless communications as a modern innovation. But, the truth is, many of the standards that dictate the quality and capabilities of your next smartphone conversation, were put in place more than a century ago. As is all too often the case, those standards were enacted following a tragedy, but endure today because they changed the way wireless technology could be regulated and used.

In 1913, the cogs of innovation engaged to pave the way for the future of wireless radio technology. The standards established at this key moment in history still form the basis of compliance for modern transmission protocols like Wi-Fi, Bluetooth, and 4G. That year, Edwin Armstrong and Alexander Meissner developed the first electronic oscillator. With it, they could modulate a carrier frequency in an efficient way. This type of transmission wave is called CW or Continuous Wave. One of the more common methods of CW communications was morse code.

While the modern world considers CW with morse code transmissions dead, the truth is that they are still alive and thriving and used for all of our favorite wireless devices.

Diagram of an Armstrong oscillator circuit using a FET as the active device.

An ultra-brief history of radio transmitters

Prior to 1913, before electronic oscillators and vacuum tubes, radio transmitters were based on spark gap and rotary spark gap technologies. These methods produced damped wave transmissions that decayed quickly and suffered massive efficiency losses. Damped wave transmission lacked a way to produce a specific frequency and had no ability to concentrate the energy within a narrow, or even practical, bandwidth.

A spark gap radiotelegraph transmitter for sending Morse code in the Electric Museum in Frastanz, Austria. (Attribution: Asurnipal, CC BY-SA 3.0 via Wikimedia Commons – https://creativecommons.org/licenses/by-sa/3.0)

Spark gap transmitters before 1900 were not all that dissimilar from a spark plug with an antenna attached. In fact, while ignition systems in cars are much quieter today, some vehicles will produce broad RF noise to surrounding devices when driving past a radio receiver such as an AM radio or even an Over-the-Air digital TV receiver.   

These types of disruptions are emblematic of the fact that much of the RF energy transmitted by spark gap transmitters ended up making noise, sparks, and spurious emissions, none of which were supportive to delivering the user’s messages to the destination in an efficient way.  

In 1903 spark gap transmitters improved with the introduction of the Alexanderson Alternator. The Alexanderson Alternator was a rotary machine that would mechanically construct a radio wave when spinning, producing a CW single sinusoidal carrier at a specific frequency.

An Alexanderson Alternator (Attribution: Gunther Tschuch, CC BY-SA 3.0 via Wikimedia Commons – http://creativecommons.org/licenses/by-sa/3.0/) 

CW allowed coding dots and dashes to be coded and transmitted by operators. Skilled operators were capable of sending 20-50 words per minute. Since then, every modern sophisticated radio product embodies CW in some way and utilizes practices set forth in 1913 including radar, broadband wireless, smart phones, and many other communications methodologies.

The birth of wireless compliance standards

One year before Armstrong and Meissner’s contributions to radio, Jack Phillips and Harold Bride sat in the radio room of Titanic in 1912 operating a spark gap transmitter manufactured by the Marconi Company. It was the most modern communication system of the time period. This device could send morse code transmissions using long and short duration sparks arranged in the dashes and dots of international morse code. The inefficiency of the transmitter still produced a lot of radio spurious emissions and noise. Other ships with similar radios nearby also suffered the same effects and radio interference was common.

The theory of operation of these spark gap devices was that power was applied to a coil that created a spark across an air gap. An antenna connected to the gap terminal and allowed resonant frequencies to propagate off the antenna. Tuning coils or matching networks improved antenna performance and early units were practical within 10 or 20 kilometers of their desired receiver. Later versions improved performance, like the one on the Titanic, could send signals up to 1000 kilometers or more.

One of the limitations of this radio is that the electric arc sizzled and cracked and made radio pulses of many frequencies all at once just the way a bolt of lightning causing broadband RF pollution across the radio spectrum. This RF could be heard line of sight as well as over the horizon from atmospheric reflections from the ionosphere or through ducting between warm and cool air propagation paths over the water.

At the time, there weren’t many transmitters in the world, but there were enough of them that it wasn’t uncommon to be running in close proximity to other stations. For the first time, radio interference between stations due to their broadband nature became a reality. There was no plan or protocol to define how many radio stations could use the limited spectrum in ways to avoid interference. When Titanic struck the iceberg, its distress calls were not heard immediately nearby because other ships were asked to turn off their radios hours before so Titanic could send passenger messages to friends and family on shore without interference from other boat transceivers nearby. The distress calls that were received were done so by ships much farther away, with limited ability to assist quickly.

The impact of the Titanic disaster on modern wireless communications

A “CQD SOS” message was sent from the radio of Titanic in 1912. CQ is a calling message (meaning ‘i am calling is anyone there?’) and CQD is calling distress (meaning i’m calling for help). “CQD SOS” was new at the time. Those familiar with CQD were possibly hearing SOS for the first time. It was heard by land and maritime stations. The problem at the time was that spark gap transmitters were trying to forward signals to land stations by relay, and all the activity was polluting the air and causing interference and inaccurate information transmissions.

Unlike modern radios that can tune to a specific frequency to listen and use another frequency to relay information, the radios in 1912 had no frequency settings and therefore could not efficiently use the same radio spectrum without making harmful interference to nearby stations. At the same time, the SOS was also a new type of message that was newly adopted by radio communities but not necessarily unified by everyone hearing it.

In response to the loss of the Titanic, the US Congress passed new rules about radio licensing and training. They also established initial radio band plans, identifying ranges of frequencies specific to certain activities. The 1912 Radio Ship Act helped license commercial and amateur radio stations paving a path towards regulations that would include standards, frequencies, band plans, and rules about reducing radio interference and interference between stations. Radio operators were now required to have the same skills of efficient operation without causing interference. Operators were to have training about how to handle emergency radio traffic.  Lastly, radios were required to be more capable of managing frequencies and spurious emissions.

Radio transmitters and radio stations still have license requirements today. Below is an example of an Intel 9260 Wi-Fi/BT module commonly found in laptops and other devices. Its radio license is circled in red and labeled FCC ID for USA and IC: for canada. The CE mark on the device also indicates compliance with the Radio Equipment Directive 2014/EU/53 (RED for short) in Europe.

This means that the radio has been tested for clean signals, that it yields to ground-to-air radar in the 5GHz Wi-Fi Dynamic Frequency Selection (DFS) band, and that the RF power is a certain limit to be safe for human and animal exposure and below a limit of harmful interference. The markings also indicates that it uses the Wi-Fi spectrum efficiently and takes turns communicating with other devices.  

An Intel® wireless card showing its FCC and IC ID numbers as well as the CE mark, indicating compliance with CE standards.

Without these rules and certifications, Wi-Fi would be unusable due to interference from the millions or billions of Wi-Fi devices running in the world simultaneously and in close proximity. Amateur radio stations, music FM radio stations, maritime stations, and more also have requirements. Some modern radio bands rely upon soft skills where operators need to know how to yield to other operators on a frequency when there is priority information. Other bands, like Wi-Fi, require explicit software control and regulation that automatically prevents data collisions and interference with DFS activity. A licensing process is used for both to maintain order and efficiency.

The lasting legacy of continuous wave transmissions

Going back to Edwin Armstrong and Alexander Meissner, they both created a way to produce undamped waves which did not decay as quickly as spark gap damped waves. At the same time, they were able to take all of the available transmission power and focus it into a very narrow bandwidth, as opposed to polluting the entire RF spectrum with energy that may never make it to the receive destination. Modern Continuous Wave or “CW” was born.

The narrower transmission bandwidth allowed more stations to occupy a given radio band (or range of frequencies) without interference between stations. Very similar to Wi-Fi, it was the origin of how priority traffic and band plans took shape.

Over a hundred years later – IoT devices are the “New Titanic”. To prevent another unfortunate catastrophe, modern radio devices are evaluated to verify radios follow protocols like proper power outputs, spectrum efficiency, spurious emissions, and that they follow a band plan.  Modern radio devices also yield to primary frequency users, meaning that important signals get priority. 

The importance of wireless communications regulations and certifications

Smart devices like mobile telephones and tablets offer two, three, or more radios in one device. In these situations, compatibility between the radios within the unit are carefully evaluated, along with other radios they may come in close proximity to. This is called coexistence or co-location testing. Testing would verify that no radio spurs are being radiated above limits in areas of the band that they are not allowed to be. Testing also verifies the functionality of the receivers and their ability to reject unwanted noise.

The 2014/53/EU Radio equipment directive, or the FCC multi transmitter protocols dictate how multi transmitter radio devices are to comply with regulations. Standards like EN 301 489 parts 1, 17, and 52, EN 300 328, and EN 301 908 start to allow methods for considering how to test Wi-Fi/BT and LTE type devices with other equipment. Other electronic equipment (such as computers or anything with circuit boards and clock frequencies) also needs to be tested as unintentional transmission devices and not to interfere with, or cause emissions that can be harmful to, radio communications.

As an example of how these regulations apply in practice, consider computers aboard ocean vessels. These systems might be doing AI, diagnostics, SCADA, machine vision, or any of a wide range of tasks that equipment aboard modern ships carry out. All of these computers need to avoid interference with ship communications and navigation systems. Evaluation to IEC 60945 or IACS E10 maritime standards assure that ship navigation and communications can run flawlessly in parallel to Edge IoT or smart devices. They may even need to operate in the control bridge next to critical communication and navigation equipment where requirements are more strict.

To look at this another way, modern devices with 5GHz Wi-Fi, for example, share the same frequencies as DFS ground to air radar. Most people do not realize that Wi-Fi 5GHz is the ‘secondary user’ of the frequency assignment in the middle of the band, and that if the Wi-Fi device detects radar activity, it is to yield and change frequencies so as not to interfere with radar. While unlikely with tested devices, untested devices could pose a risk for air transportation that could lead to terrible consequences with air traffic. This is why it is important to know if your wireless IoT device is working properly and within the established standards.   

OnLogic’s expertise in wireless technology

OnLogic specializes in radio devices and has the expertise and equipment to evaluate transmitters and understand compatibility and usage environments. As experts in the field, OnLogic understands global wireless requirements. All core systems are evaluated for multiple transmitters and multiple countries so that our customers can be assured they are fully in compliance to current radio and computer safety and emissions requirements.

OnLogic follows international emissions standards such as CISPR 11, CISPR 32, and CISPR 35 for emissions and immunity testing. Devices are also tested for maritime radio and navigation compatibility according to IEC 60945.  Radio compliance adheres to all of the requirements to the Radio Equipment Directive 2014/53/EU. We recognize the importance of stability in all of the radio protocols being used in the harsh environments our systems are frequently placed in. Extensive testing is performed, including 2x to 30x (test dependant) the required immunity limits required for CE in the European market. The wireless technology solutions provided are as acid tested as the most rugged computers we offer.

While this may sound like alphabet soup to the average computer user or even radio communications enthusiasts, I find it fascinating that over 100 years after Titanic’s fateful night, current radio devices like smartphones and tablets are all tested in highly advanced radio labs using the most modern spectrum analyzers and techniques, all while using the original transmission modes that Jack Phillips and Harold Bride specialized in — CW.