Is CW a true, pure digital mode?

Discussion in 'Working Different Modes' started by KC0BUS, Apr 2, 2019.

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  1. KQ0J

    KQ0J XML Subscriber QRZ Page

    Not to the FCC.
     
  2. W5LZ

    W5LZ Ham Member QRZ Page

    Yes, a very slow one...
     
  3. KA9JLM

    KA9JLM Ham Member QRZ Page

    I have a digital antenna. And digital headphones also.
     
    ND6M likes this.
  4. W9NPI

    W9NPI Ham Member QRZ Page

    CW is the label for the Continuous Wave mode. It was an improvement over the Damped waveform produced by spark transmitters that originally produced radio waves. Damped waves were known by the shape of a keyed pulse--a power surge that slowly died out. CW was an improvement, allowed something very close to a digital On/Off, and could be produced in at least 3 ways:
    1. Mechanically, with a high speed alternator, good to ~100KHz;
    2. As a continuous Arc (the radio wave needed to be shifted to another frequency as it was keyed--it was FSK;
    3. through a vacuum tube or transistor oscillator.

    All three of these modes could be Voice Amplitude Modulated, although Fessenden experimented with a modulated spark around 1901.

    --from W9NPI's lecture at AWA: History of Telegraphy, Part 2.
     
    K4AGO likes this.
  5. WA3VJB

    WA3VJB Ham Member QRZ Page

    Scott Fike KC0BUS, has asked more than 1,000 questions on here the past 15 years. Most are open-ended, vague like this one, and he rarely shows any sign of making use of the information. One thread he initiated appeared to be a topic he could be planning to write a book about. Thus, with all the responses he's got to all his questions, we could be helping write such a book for him, the theory goes !!!
     
  6. ND6M

    ND6M Ham Member QRZ Page

    Well, then it depends on the particular operator, I seem to get many QFL type comments.
     
  7. W0AEW

    W0AEW Ham Member QRZ Page

    He does open up discussions that are quite interesting, IMO. Whether he joins in the discussions he starts is immaterial.
     
  8. KD0KZE

    KD0KZE Ham Member QRZ Page

    In a theoretical, mathematical and logical sense, you don't need a computer for a mode to be digital. Unless you want to call basically anything that can process digital data a computer -- whether electronic, mechanical or maybe even biological. I'm game for that. I'm sure we can point to several historical examples, and many may not quite qualify as Turing machines, but they can encode/decode digital type data at a primitive level.

    CW is not encrypted, but certainly encoded. A digital mode needn't be binary. Trinary would be fine also, probably any number of states so long as it was discrete. As for the time element, CW additionally spaces letters to the time equivalent of 3 dits, and word spaces equivalent to 7 dits.

    I suppose you could skirt the time requirement if you tweaked CW a little to actually use 4 tones: one for dit, one for dah, one for a character space, and one for a word space. Though you wouldn't be able to use a normal telegraph key if you needed multiple tones.

    But you could skirt the time requirement with a different sort of tweak. Make all "bytes" of equal length, with a separator. Each new byte would automatically suggest a character space. A special byte would be the spacebar space (word space). Right now, the longest CW character is 5 bits (the numbers). Heck, you could go to 7-8 and get CW ASCII. :) And here we are.

    I suppose whether your data is stored on primitive memory cores, modern chips, or radio signals, what's essential to be able to measure a change of state from bit to bit. In physical devices it would often be across space (on physical media, memory addresses, etc). With radio, the state change seems to pretty much always be related to time, though you could at least render the spaces all equal between bits to make matters easier.

    73, KD0KZE / Paul
     
  9. AF7TS

    AF7TS Ham Member QRZ Page

    All signals are analog signals. You transmit by changing some parameter of a system, say voltage, and you receive by measuring that parameter. The transmission is never perfect, the channel introduces noise and attenuation, and the receiver introduces noise and distortion.

    What makes a signal digital is that it is rendered discrete in the modulated parameter and in time. As long as the original discrete intent can be determined, the signal can be regenerated perfectly. In other words, if you can figure out if a 1 or 0 was sent, you can resend that 1 or 0.

    With this understanding, one-off keyed Morse is most certainly digital. The on or off is clearly binary, but so is the timing. You are either on or off for a duration of one for time.

    A for is on for one for time then off for one. A day is on for three then off for one. Between letters you add more off time and between words still more.

    So the letter e is encoded as 1000. S is 1010100. O is 11101110111000. L is 10111010100 LOST is 10111010100011101110111000101010001110000000

    I've often thought that bpsk could be used to carry morse and be human readable with a simple demodulation circuit.

    73
    _Jon
    AF7TS
     

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