Resilient CW in Marginal Conditions

Submitted by Lou VK5EEE of
Communicators Without Borders

Resilient Communications: Morse Adaptation in Poor Propagation Conditions

Cw at 12WPM can be copied down to -12dB SNR @ 2500 Hz and lower SNR with repeats and slower throughput, e.g. down to -26dB QRSS. Ref:

An important skill in resilient communications is the ability to adapt Morse code to propagation including QRN and sub zero SNR to achieve effective throughput where otherwise there would be none. A small minority of cw operators have perfected this skill by hand crafting every dit and dah at QRS, the best example I can think of with this skill is Rob, VK2MZ, a former maritime radio officer. If Rob cannot get a message through in the most difficult of conditions using cw, no one can.

The technique involves keeping information short (i.e. leaving out greetings and pleasantries and using Q codes and sufficient repeats, e.g. RRRRR or QRG? or QRK3 QRK3 or QSY etc, use of QSK and a keen ear. A variation of the technique can include numerous repetitions of individual letters e.g. VVVVV KKKKK 22222 MMMMM ZZZZZ. Cw signals down to -13dB SNR or so may be copied and complete messages exchanged via such techniques even during short-wave fade outs, geomagnetic storms, or high local noise or atmospherics i.e., QRN.

?????? KKKKK



Cw remains the only mode that does not require a computer or decoder of some sort, but, by slowing down at a predictable speed, and increasing the internal character spacing, and using the techniques that Rob VK2MZ perfected during his many years of cw operation including at sea, one can really achieve communications where even most cw operators would give up. Rob and I have always delighted in persisting in the completion of QSOs with any QRK above 1 with radio amateurs who will practice such marginal QSOs with RST of 229 to 339, or anything above RST 100.

This skill is essential to being able to communicate during an EMP or severe solar event that may knock out the grid and most electronic equipment, and all that may remain are QRP stations that were preserved in Faraday cages. Take a look at the QCX transciever kit and start building: it is, for $49, a single band (any 80-15m) rig that has features of ten to one-hundred times price.

The built-in straight key is perfect for QRS cw but it also has built in keyer, test equipment, dual VFO, split, RIT, filter, and the receiver is way less susceptible to local noise than most super hets. Also built in are cw decoder, frequency and message memories that can be programmed even by non-cw ops for emergency use, WSPR TX.

I’m currently working with the creator on building into the firmware, at least as an option, an emergency cw <SOS> mode including the “Auto Alarm” that former sparks, meaning maritime radio officers, were familiar with, possibly with enhanced features such as optional recognition of CQ or call sign being called, thus the volume could be down and an alarm sounded upon reception of an urgent or specific call.

At that price, building more than one QCX so you have spares, or more than one band capability, is a good idea. Keeping a spare in a Faraday cage should not be a difficult task, for preservation in the event of an (N)EMP. Keeping a stock of alternative power supplies, solar chargers, would also be a good idea. The QCX runs at any DC from 7V to 18V with current draw on TX at 5W being around 0.5A, and around 100mA on receive.

Practising and perfecting weak signal and low signal to noise ratio cw is an important part of building a resilient communication network of trained operators, as is the passing of messages in a fixed QTC format which allows for 100% reliable transmission with “filler” repeats and built-in checking/verification systems such as word count or “check.”

The USA government recently conducted an exercise simulating the expected event where communications including the web, computers, electronics will be knocked out, and 97% of the population may be expected to perish miserably within one year of loss of power. AUS would not fare much better. Those who are fatter and most comfortable now will fare the worst. Lose weight, increase personal, family, equipment and communication resilience and prepare for an event that did occur around the era of early telegraphy and would have causes a near world-wide blackout in today’s world.

RESILIENT COMMUNICATIONS is what Communicators Without Borders and our partners at RRI Radio Relay International are all about — please consider joining RRI today.

Join in our various cw nets to practice, or at least check in with a QRU, to familiarise with cw nets in your area and the frequencies and schedules to turn to in the event of disaster or a communications emergency.

We are considering an exercise for Australia to check the ability of radio hams using cw to operate during simulated SHTF or TEOTWAWKI conditions, perhaps at short notice.

Comments welcome!

73 es 77 de Lou VK5EEE

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