CW vs PHONE FOR DX

Discussion in 'General Technical Questions and Answers' started by K1KTF, Mar 27, 2020.

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  1. K1KTF

    K1KTF Premium Subscriber QRZ Page

    Hi Ham Friends: Warning - Kind of a dumb question that I should already know:)

    My son asked me which travels further, CW or Phone and why. I know this was in study theory but was looking for a basic answer. Josh is becoming more intrigued with CW since I’m using this mode more often for dx.

    Again, I apologize in advance for the question.

    Stay Healthy, Happy and God Bless.

    73 ~ Steve (K1KTF)
     
    N2HUN likes this.
  2. W4HWD

    W4HWD Premium Subscriber QRZ Page

    CW is narrow, phone is wider. The mode that uses less bandwidth, at least theoretically makes it through better under all conditions. The biggest factor assuming propagation exists between the two stations would be the receiver, antenna and operator on the other end - plus the size of the pileup.

    I’ve successfully worked stations with 100w on CW that I couldn’t get to at all with 1000w on phone.
     
    K1KTF, K9CPO, KC3RN and 2 others like this.
  3. N2HUN

    N2HUN Ham Member QRZ Page

    Steve this is an excellent question. CW is always better for DX or when conditions aren't the greatest One reason is that it's just easier to hear and decipher dots and dashes versus the inflections and different tones of the human voice.
     
    K1KTF, N7EKU and W5WTH like this.
  4. SM0AOM

    SM0AOM Ham Member QRZ Page

    There is a very simple answer to this, which is related to the signal energy required to keep communications. A question that has been investigated since the 1930s.

    upload_2020-3-27_11-56-27.png

    "CW" or Morse (A1A) requires a normalised signal to noise ratio (SNR)
    of 31 to 38 dB/Hz and "Phone", which here is assumed to be SSB or J3E in ITU parlance,

    upload_2020-3-27_11-59-27.png

    requires an S/N in the region of 47 t0 50 dB/Hz to be "just usable".

    The difference is about 12 to 15 dB, or expressed as a power ratio 16 to 30 times. So, everything else being equal communications can be upheld with, say, 5% of the RF power by using Morse instead of SSB "Phone". Morse also requires less bandwidth.

    How this translates to actual communications range is much harder to say.
    No simple relationships exists between required RF power and range on HF, but there are some "rules of thumb" around in the business.

    I have a background in commercial and military Air/Ground HF SSB systems design and operations, and in the early 1970s, there was a shift between AM and SSB for oceanic Air Traffic Control. This was before my time, but I met senior people that were instrumental in this transition.

    The difference in required RF power for the same "grade of service" between AM and SSB is about 8 dB or 9 times. When deciding the channelling plans and placement of ground stations, the maximum practical service range for SSB was considered to be about double as compared to AM.
    This could also roughly be said of the difference between Morse and SSB.

    Finally, Morse is always superior to "Phone" in amateur radio, as it is "character building" (pun intended) and creates better radio amateurs.

    For these reasons, the abolishment of the universal Morse knowledge requirement was a mistake of epic dimensions.

    73/
    Karl-Arne
    SM0AOM
     
    N1OOQ, K1KTF, K9CPO and 1 other person like this.
  5. KK4NSF

    KK4NSF Ham Member QRZ Page

    I concur. Just recently we learned that the US Coast Guard is abandoning CW. They were among the last to teach it as a back-up mode.

    But you know, we as a group are excellently positioned to keep Morse alive, and spread the knowledge to others.
     
    K1KTF likes this.
  6. AI3V

    AI3V Ham Member QRZ Page

    2 reasons, that are interrelated.

    First off, there is much more "information" in somebodys voice than in a simple on/off code.

    When you hear somebody, you can generally tell if tgey are man or woman,
    Big or small in size (know any 90 pound women who sing bass?), often you can tell what part of the world they are from (accent), or what their native language is.

    Basically, you can tell your brother Bob from aunt Peggy.

    This takes bandwidth.

    Now, the second part is that noise is more or less equally spread across the band, if you have a signal that requires more bandwidth, your receiver will naturally pick up more noise.

    Search "KTB Noise" for more info about bandwidth vs noise.

    ......

    A curious thing happens to speech as you restrict its bandwidth further and further.

    After a point, you can still understand what is being said, but everybody sounds alike (and somewhat mechanical, or artificial)

    You would find this unacceptable for most communications needs.

    Rege
     
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  7. K4SAV

    K4SAV Ham Member QRZ Page

    There is even a larger difference for someone with high frequency hearing loss. Speech is difficult to understand even when the signal to noise ratio is good because most of the intelligibility is in those high frequencies. With CW you can set the tone to something you can easily hear.

    Jerry, K4SAV
     
    WW2PT, K1KTF, W9JEF and 1 other person like this.
  8. N7WR

    N7WR Premium Subscriber QRZ Page

    When I as trying to finish DXCC on 40 and 80 from the west coast with only wire antennas on those bands I found I could work EU and AF much easier on CW than SSB. That is why my now 7BDXCC and Honor Roll are mixed not just SSB
     
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  9. WA4ILH

    WA4ILH Subscriber QRZ Page

    Rege makes an excellent point however:
    The only voice frequencies that are absolutely necessary for communications is in the range from about 400 Hz to 2,400 Hz. This distinction is important because there is a considerably larger amount of power in the range not needed for communications below 400 Hz, about three times more power in some adult males. If you filter out all of the unneeded “power” of the voice spectrum below 400 Hz, you greatly reduce the amount of unnecessary audio power and increase the essential higher voice frequencies being fed to the balanced modulator. The down side is, of course, it sounds tinny.
    Tom WA4ILH
     
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  10. N4UP

    N4UP Premium Subscriber QRZ Page

    Agreed. Although there is also "some" additional information contained in the CW rhythm/style and combination of other subtle factors ( e.g., speed, spacing ), so with experience you can actually recognize someone by the "way" they send CW.

    Granted not as much information as in a solid SSB signal, but many can recognize weak signal "fists" fairly well.
     
    K1KTF likes this.

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