CW Radiotelegraphy – A disaster surviveable mode
Marconi used Morse code to conduct the historic maiden radio contact. The transmission of Morse code over the radio waves thereafter became the standard method of radio communication. All other modulation modes like radiotelephony etc came into existence much later. With the advancement in technology, many different modes of information modulation over the radio were developed over the centuries. However, Morse code transmission over the radio, despite its early genesis, due to its sheer simplicity and requirement of minimal equipment complexity continues to remain the most robust mode of radio communication to date.
Morse code radiotelegraphy is popularly known as CW (continuous wave), or CW Radiotelegraphy. In the event of a widespread catastrophic disaster, when all other methods of radio communication might fail, CW Radiotegraphy communication link may have the greatest possibility of surviving.
CW Radiotelegraphy in Amateur Radio
Traditionally, since the inception of amateur radio, over many decades, CW Radiotelegraphy has remained an important aspect. Voice modulation methods gradually gained ground with the advent of amplitude modulation (AM) followed by frequency modulation (FM), Single Side-band suppressed carrier AM known as SSB, etc. Digital modulation methods have taken the amateur radio world by storm in the 21st century which has led to CW Radiotelegraphy taking a relatively backseat in the present day and age. However, the significance and relevance of CW cannot be dismissed even now.
Some of the major highlights of CW Radiotelegraphy are as under…
- Establish communication with the simplest hardware for transmitting and receiving.
- Requires a narrow bandwidth thus allowing effective communication over a cramped radio spectrum.
- Low transmitter power requirements to establish communication over long distances under difficult conditions.
- Very weak CW signals are readable under poor SNR conditions and noisy communication environment.
- Complex signal processing in transmitter or receiver is not needed for thus rendering the equipment to be more reliable.
- The human brain which is perhaps one of the most adaptive information processors in the world uses its unique faculties to decode CW and discern the received signal and isolate it from various forms of interferences. The abilities of the human brain are unmatched.
- Under emergency conditions a makeshift CW transmitter and receiver can quite easily be put together with minimal components to establish radio communication. CW Radiotelegraphy is typically a standalone mode that unlike most of the modern low-power/weak-signal digital modes does not require support from other machines or computers to function.
In view of the above factors, the importance of CW Radiotelegraphy must not be undermined. Not only does CW serve so well under emergency situations but it is also a great spectrum efficient and low-cost method of establishing global communication during normal times. Especially on the HF radio frequency bands, the amateur radio operators with CW skills spend countless hours communicating with other operators around the world.
Why is amateur radio CW Radiotelegraphy sadly on the decline?
The primary reason for the gradual decline in interest about CW is perhaps the fact that it is prima-facie seen to be a code based language, unlike the natural languages that we speak. There is a general resistance among new radio amateur to put a bit of extra effort to learn Morse code. In the earlier days, everyone had to learn Morse code and attain a reasonable proficient in sending and receiving Morse code. However, with the passage of time, the licensing requirement for radio amateurs around the world have gradually been relaxed. In several countries now, CW is no more mandatory to apply for certain categories of licenses. This has led to the removal of motivation for aspiring amateurs to learn CW anymore.
I believe that this is rather unfortunate. I also believe that the usual difficulties faced by new operators to attain proficiency with CW were more to do with the incorrect methods that were used to teach it. There has been a general tendency to present Morse code (CW) as a set of code sequences of “dits” and “dahs”. At the learning stage, the students have invariably been presented with a Morse code chart to memorize and familiarize themselves with the codes. In my opinion, it was a fatal approach.
How to learn CW Radiotelegraphy effortlessly?
Although, Morse code has a structure of unique combinations of “dits” and “dahs”, it should never be leaned by memorizing the codes. CW should be treated as a language and not as a code. Just like any other spoken language that one might learn by listening to the sounds of a word, CW also must be learned as language comprising of a set of sound sequences representing each character. This makes CW a far easier language to learn in comparison to any foreign spoken language.
Unlike a typical new spoken language where one might need to learn at least a couple of hundred words to get going, or perhaps a few thousand words to attain proficiency, CW is far more simple and easy. Every alphabet, numeral, and punctuation mark has a distinct code resulting in a very distinctive sound. The swing of the sound of each CW character is like a musical note, each of these note sounds distinctively different.
The idea is to learn each character by listening to its distinctive musical sound sequence as a whole and registering it in the mind by associating it with the character. Forget the dit-dah composition of the character. Don’t think about a CW character in terms of its code. Doing so is the biggest blunder that one could make… Unfortunately, that is exactly the blunder that people have been (and been asked to make) while learning CW.
One needs to learn only the unique sound sequences of 26 alphabets, 10 numerals, and approximately another 8-10 punctuation marks and pro-signs, etc… That is all that is there to learn CW. Only a total of 44-46 distinctive sounds that one needs to learn to discern and identify mentally. The total vocabulary of the language called CW is only around 45, as against several hundred or thousand in the case of a new spoken language. Once a person becomes comfortable at identifying these 45 different sounds and through a little practice when it becomes second nature, Voila!, he has now learned CW. In fact, when a person has attained adequate proficiency with alphabets and numerals only, totaling up to 36 characters, he is well set to copy most CW QSOs.
Another grave mistake that people learning CW are made to make is by advising them to learn it at a slow speed first and then gradually build speed. Such a piece of advice is poison. Those who are exposed to this poison during their early learning days never ever become great CW operators. Just as a toddler effortlessly learns to speak by picking up words that he would hear being spoken in his household environment, the CW learner (like a toddler) needs to be exposed to the sounds of CW to be able to learn it effortlessly. This is the nature of the human mind.
The parents of a toddler in the house do not speak at very slow speeds, neither do they drag and stretch words to make them sound in slow-motion for the benefit of the child. They go around speaking normally and the child easily picks up those words gradually and learns to understand them and eventually speak. The same applies to the learning of CW… Do it the natural way and you will be surprised as to how easy it is to learn CW.
Just like one learns new words by listening to them are the normal rate of speech, try to learn CW by listening to the sounds of character at a comfortable normal rate. I would suggest that one must start learning CW by listening to the character sounds typically at a comfortable speed of around 20 WPM. Don’t ever fall into the trap of learning at slower speeds like 5-6 WPM, or whatever.
While learning any language, obviously one is not expected to follow all the words of that language initially. One would start with simpler sentences with common words. Similarly, while learning CW, don’t start by listening to sentences with a combination of all the 45 characters but begin with a random set of 2-3 characters for a couple of days.
Thereafter gradually add another 2-3 new characters to the existing ones until you can comfortably distinguish between all of these 4-6 characters. Gradually keep adding a few more characters after a few days or a week. Eventually, after a few months, you will discover that you have learned all the 45 characters of morse code. You can now sit comfortably in your armchair and listen to a stream of regular words and sentences being transmitted at 20-25 WPM. You won’t need to make an effort to decode them. Your brain will automatically start flashing the decoded characters one after another as they flow through.
After some practice, the mind will not only pick up the CW characters from the flowing transmission but will also subconsciously combine them to form words. Without even thinking, the complete words as they flow through will get formed in your mind. The human brain has fantastic abilities. We only need to unlock them by learning CW the proper way.
Finally, do not attempt to send CW till the time you have learned how to receive CW comfortably. It is only then that the proper sounds swing of each character will be ingrained in your mind. They are like accents. When the brain has learned the proper sound accents of every character, only then you should try to use the key to practice sending. The advantage would be that now you will never send poor and badly accented CW. Your brain won’t let you do it because it knows the proper accent and prevent you from making a mistake while keying.
Here is a minimal CW Morse code chart of characters that one needs to learn to start off with CW Radiotelegraphy. Of course, a few other punctuations and prosigns also need to be learned to achieve proficiency but this is a good starting point. The list consists of just 39 characters to get one started. Please remember to use this chart only as a reference. Do not try to memorize the pictorial combination of codes. Always learn to follow the character sounds and let the brain do the rest.
I will present practical CW learning techniques along with MP3 lesson files using the Farnsworth method (to be covered separately) for learning it in a separate article under this section.
What makes CW Radiotelegraphy such an outstanding mode?
CW Radiotelegraphy is indeed an outstanding radio communication mode. It is not only spectral efficient requiring relatively lower RF power to establish effective communication, but it also requires far lower hardware overhead than any other radio communication modes. The equipment need not be complex. The transmitter and the receiver chains are simpler in design.
Moreover, the transmitting equipment is far more efficient. Unlike most modulation modes, barring the FM, the CW transmitters do not need linear amplifiers in the RF power chain of the transmitter. A far more electrically efficient class-C or class-E PA does the job. This results in smaller sized equipment that runs cooler with minimal power wastage.
The occupied bandwidth of a CW Radiotelegraphy signal is only a fraction of what is needed for SSB Radiotelephony. As a consequence, perhaps a dozen communication (QSO) can simultaneously carry on within a segment of bandwidth needed for a single SSB QSO. This becomes quite useful when operating under congested band conditions especially when the HF radio propagation conditions are good and signals from various stations around the world manage to cover long distances around the world.
Due to the narrow bandwidth requirement for CW Radiotelegraphy QSO, one would typically use a narrowband receiver filter. This will go a long way towards reducing adjacent channel interference and also might reduce desensitization of the receiver and reduction in adverse effects of 3rd order intermodulation distortion.
Copying CW transmissions by the ear makes it possible to copy far weaker signals with Signal-to-Noise Ratio (SNR) as low as zero, whereas most other modulation modes including most digital modes might require a minimum SNR of 4-6 dB at the least to ensure a reasonable copy. A 100% copy on these modes might require a much higher SNR to the tune of 8-10 dB. The ability to copy CW Radiotelegraphy under conditions of hostile fading (QSB) is also far better, thanks to the ability of the human brain to adapt and cope with the effect.
Minimal equipment requirement for robust CW communication
Radio wave modulation for CW Radiotelegraphy is fundamentally a very simple process. The RF carrier is keyed to produce an interrupted sequence of RF bursts in accordance with the structure of the Morse code thus producing a stream of “dits” and “dahs”. This is also termed as Carrier On-Off Keying (OOK). Though we tend to believe that digital radio communication came into being as the technology evolved over the decades, the fact of the matter is that CW Radiotelegraphy happens to be the earliest form of true digital communication mode.
The Morse code symbol states and consequently the RF output of a CW transmitter is truly binary in nature. The only difference between what we call modern digital modes and CW is that CW is a human mode requiring only no additional machine or computer, while other digital modes are machine modes which can neither be encoded nor decoded without the aid of machines or computers.
The binary OOK method of CW makes it so simple to generate. CW RF modulation can be produced simply by keying an oscillator or keying any subsequent amplifier stage in the transmitter chain. Unlike the radiotelephony transmitters, the RF amplifiers need not have a linear amplitude response. Therefore, the more efficient non-linear response class-C amplifiers can be used very effectively in CW transmitters. This is how CW Radiotelegraphy transmitters were designed since the inception of radio communication.
The modern-day multi-mode radio transceivers that we generally use these days follow a radiotelephony first approach. They are primarily designed for radiotelephony modes like SSB, while CW mode is incorporated as secondary to fit the design paradigm. Therefore, modern transceivers that always have linear RF amplifiers in their transmitter chain use a roundabout way of producing CW. This works well but it is relatively more complex and rather more inefficient. A dedicated CW transceiver on the other hand, though it cannot process SSB radiotelephony is far more efficient, simple, light-weight, and robust in comparison to a general-purpose multi-mode transceiver.
The earliest CW RF transmitters during the days of Marconi did not even use any active electronic device. Only passive components like inductors and capacitors were used to produce CW Radiotelegraphy signals. It is true that such a barebone antique system did not meet the modern standards as required for a clean RF generation but in principle, it worked.
Later, over the coming decades, active components like vacuum tubes and transistors were used as RF power oscillators where only one or two tubes or transistors could form the entire CW radio transmitter. They could be either based on LC tuned VFOs or for the sake of frequency stability they could use quartz crystals. To improve the spectral cleanliness, low-pass RF LC filer chains were often used at the output of the transmitter. All said and done, a decent workable CW Radiotelegraphy transmitter was (and is) far simpler in architecture and can, therefore, be easily assembled in emergency situations to establish radio communication.
Similarly, though the modern superheterodyne receivers, the SDR, etc are all perfectly suitable to receive CW, the very basic receiver with far less complexity may also be used effectively especially during emergency situations. A simple regenerative or super-regenerative receiver assembled out of only a handful of discrete components can provide enough sensitivity and selectivity to be able to receive CW Radiotelegraphy if needed. The ability and skill of a radio amateur to hook up such a receiver along with a simple CW keyed transmitter using components available off-the-shelf, junk-box, or by cannibalizing standard domestic broadcast radio sets, etc is what makes CW Radiotelephony so awesome and dependable.
This is a mode of communication that might be the last resort in a situation of a dire emergency. A simple 0.5-1W power output CW TXR can easily be built this way which may be able to communicate over the HF bands across hundreds of kilometers or even several thousand kilometers depending on the propagation conditions.
However, it does not mean that CW is only an emergency communication mode. It is a regular mode of radio communication that is practiced by tens of thousands of radio amateurs around the world on a day-to-day basis. They do it because they love it. They like the soothing musical sound sequence of a CW transmission and have the skills to copy it by the ear just like any other spoken language.
Some of the modern, high performance, multi-mode amateur radio transceivers might cost several thousand dollars. They are complex in design and are relatively large in size and require a separate power supply unit and additional hardware to perform optimally. As a consequence, the overall system is more fragile and prone to breakdowns. They need to be handled with more care. In the event of a breakdown, a radio operator would most probably not be able to repair it in a field environment. The rig would need to be sent back to a service center.
On the other hand, a modern dedicated CW radio transceiver that puts out 5-10W RF power may cost just a hundred dollars or a little more. The effective communication range capability of a 5-10W CW transmitter is no less than that of a typical 100W PEP high-cost multi-mode HF transceiver. The reason is simple. A typical barefoot multi-mode HF transceiver outputs around 100W PEP. The 100W PEP SSB uses a typical modulation bandwidth of 2500 Hz. On the other hand, the bandwidth for CW is around 150-200 Hz or even less. Due to this, the CW has about 11-12 dB advantage over SSB. This implies that 100W PEP SSB will for all practical purposes have a similar capability as 6-8W CW if the receiver is well designed and has a proper narrowband filter.
Although I do not endorse any product, here is an example of a readily available and very high-performance CW transceiver. It cost only USD 49 in its basic form. The overall cost is less than USD 100. It produces 5W CW on HF bands and has a builtin digital filter system to provide a detection bandwidth of 200 Hz for receiving. This CW TXR uses a modern digital synthesizer as the local oscillator and a quadrature digital sampling detector (Tayloe) front-end. It provides excellent sensitivity, dynamic range, IMD characteristics. It has a digital frequency display with a digital S-meter and also has a basic CW-Text digital decoder. This microprocessor-controlled CW TXR is 8 x 10 cm and can be comfortably carried in the pocket. Although it has a builtin on-panel microswitch Key, it can support external straight key as well as a paddle. It can be used with any low-cost mobile phone earplugs. It can be connected to any 12V battery and a wire antenna like a simple dipole to provide full performance.
The above example of a miniature and a robust pocket-sized high-performance CW TXR goes on to highlight the fact that robust CW communication can be established with minimal hardware under any condition from any location if the need arises. CW is a mode of radio communication that must not be trivialized even though we have various other wonderful modes at our disposal. These modes are great under regular circumstances but it is CW that could ultimately be the savior under situations of a dire emergency.
In my opinion, all amateur radio operators must make it a point to develop CW operating skills by learning to send by the key and receive by the ear even though their licensing requirement might not need them to do so. Only then, we can truly claim to be a community that can step in to help deal with communication needs during a disaster. Without CW skills, our claim that the amateur community plays a great role during a disaster is all humbug and a misplaced sense of self-glorification that is destined to fail when the world might need it the most under conditions of extreme disaster scenarios or catastrophic global emergencies.
Why is CW Radiotelegraphy the ultimate disaster survivable mode?
Yes, CW is perhaps the only mode that might survive the conditions of extreme catastrophic large-scale disaster when all other radio communication modes might fail one after another. Let us examine why…
When I speak of Ulitimate Disaster survivability, I do not refer to the regular types of emergency situations caused due to floods, cyclones, earthquakes, etc. Most governments around the world have adequate action plans and resources to deal with grave situations under these circumstances. Of course, we amateurs also step out and providing a definitely useful helping hand. However, the role of amateurs is secondary. We assist as additional communication manpower to help the authorities.
However, a catastrophic world-wide disaster may be a different story altogether. Such a disaster could be either natural or man-made. The last time we face such a situation was during World War II when some places got completely devastated by widespread destruction. One after another, cities and towns turned into rubble and the local governments we in absolute disarray and completely helpless. All communication infrastructure in those regions were uprooted. That’s when radio amateurs played a vital role.
God forbid, if such a situation were to occur again in the 21st century, then the magnitude, as well as the nature of the catastrophe, would very different. It would be something that we perhaps cannot even imagine. A nuclear-armed world that is heavily dependent on the Internet and an extremely vulnerable satellite networks that could be taken down by Anti-Satellite weapons would render all modern high-technology communication systems and networks defunct.
Governments will be in disarray and all modern communication systems for public use will be down. There will be no cell-phone and no Internet. The amateur radio emergency services as we have today will largely be unsustainable. The VHF/UHF repeater networks would have been knocked off. No Internet would mean no Echolink, etc. The radio rigs and antennas at our QTH might also be damaged.
The bottom line is, that come what may if such a catastrophe were to ever occur, it is only CW that might come to the rescue of mankind. This is the reason why, we the radio amateurs must all develop and maintain adequate CW skills, each one of us, at all times.