Ham Radio - Modulated CW with FLdigi, not A2A. How it works, and is it wider than regular CW?

Discussion in 'Amateur Radio News' started by KB7TBT, Nov 23, 2019.

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  1. KB7TBT

    KB7TBT Ham Member QRZ Page

    Ham Radio - Modulated CW with FLdigi, not A2A. How it works, and is it wider than regular CW?

     
    KK4HPY, GM0GTU and PY5ME like this.
  2. KU4GW

    KU4GW Ham Member QRZ Page

    Unfortunately MCW (Modulated CW) is only permitted on VHF, UHF, and SHF. Part 97 FCC rules say it's not allowed on the HF bands in the U.S. See 47CFR §97.305 Authorized emission types + any notes specified in the right margin beside of each band in the tables in 97.305, then refer to 97.307 Emission standards to interpret the notes. What KB9RLW is doing is illegal according to Part 97 FCC rules & regulations since he's transmitting MCW on the 20 meter HF band. That's what I interpret from reading the rules anyway. Please correct me if I'm mistaken and if so tell or show me how. Just trying to play it safe! http://www.arrl.org/part-97-text
     
    Last edited: Nov 24, 2019
  3. W1AET

    W1AET Ham Member QRZ Page

    Just because you can, doesn't mean you should.
     
    N2EY likes this.
  4. K7JEM

    K7JEM Ham Member QRZ Page

    It's unfortunate that in the video the presenter used the term "modulated CW", which is incorrect. An audio tone inserted into an SSB transmitter produces regular CW, by definition. Modulated CW is where an AM or FM transmitter is fed an audio morse code stream. It produces a carrier and sidebands, which is much wider than regular CW.

    From the definition of CW in part 97:

    (1) CW. International Morse code telegraphy
    emissions having designators
    with A, C, H, J or R as the first symbol;
    1 as the second symbol; A or B as the
    third symbol; and emissions J2A and
    J2B
    .

    FLDIGI produces J2B when attached to an SSB transmitter. If you took a code practice oscillator with a key attached, and fed that into an SSB transmitter, you would have J2A. Both of those are defined as CW, and are the same, for all practical purposes.
     
    N8CDW, KB8NXO, AF6SA and 11 others like this.
  5. KK5JY

    KK5JY Premium Subscriber QRZ Page

    @K7JEM is quite correct - there is certainly nothing wrong with using a tone to modulate an SSB transmitter to produce CW. In fact, this method has some advantages if done properly, because the modulating wave shape can be very precisely controlled to minimize key clicks, etc. To emit a clean signal, one does need to be careful not to overdrive the transmitter audio stages, avoid compressors, etc.

    If you want to operate CW from fldigi, there is a simpler way to do so that is almost certainly guaranteed to be cleaner for most newer radios. The fldigi manual describes a simple circuit that allows the sound card to hard-key the CW input of your transmitter. I updated this circuit to use more current parts, but either way, using a keying circuit allows one to use one's radio in the dedicated "CW" mode, which lets you use CW-specific filters and features, while still using fldigi for both transmission and reception.

    If you use a radio that has a dedicated hard-key input for RTTY, this circuit can be used for RTTY, too. Just like with CW, this has the benefit of allowing you to use the dedicated RTTY features of your radio, like special RX filters, etc.
     
    KK4HPY, NN4RH and W4RAV like this.
  6. W5WTH

    W5WTH Ham Member QRZ Page

  7. ND6M

    ND6M Ham Member QRZ Page

    I think he is running 0.5 watts into a dummyload.
     
    N8JLM likes this.
  8. W3ATT

    W3ATT Ham Member QRZ Page

    I also agree with K7JEM. If you're on frequency with another station sending CW over SSB using an audio tone (from FLDigi in this case,) you would never know the difference. There is no carrier being sent, just the audio signal which you can zero beat like any other CW station.

    I was experimenting with this back in 2012 when I used to run PSK31 with FLDigi. I decided to try the CW mode through the sound card interface.

    When set up PROPERLY (not triggering ALC whatsoever,) I could drive the radio from QRPp levels to full power output by simply keeping radio set to full power output and varying the audio input through the sound card interface. And the reports of my CW "note" were outstanding since, as KK5YJ mentions, "the modulating wave shape can be very precisely controlled to minimize key clicks, etc." And if you listen to the CW audio coming from FLDigi, it sounds just great.

    The only problem I have with typing CW is that I just can't seem to type as fast as I can key LOL!
     
    K0PV, N8JLM, W4NNF and 2 others like this.
  9. KU4GW

    KU4GW Ham Member QRZ Page

    Thanks for the info Joe!

    Very 73 & Happy Thanksgiving!



     
  10. N5TZH

    N5TZH Platinum Subscriber Platinum Subscriber QRZ Page

    why not just learn cw and use a key if you need a computer to run cw mmm something not right about that
     
    K0PV, SIMPO and N4EEV like this.

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