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JS8CALL (FT8CALL on Steroids) 20wpm - 24 db / Jordan KN4CRD does it again!

Discussion in 'Amateur Radio News' started by NN2X, Oct 7, 2018.

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  1. K9EQ

    K9EQ Ham Member QRZ Page

    This appears to be comparing apples and oranges. It is critically important to specify the bandwidth over which the measurement was taken. In the case of the PSK31 article, the bandwidth was 100 Hz. The WJST-X modes use a bandwidth of 2,800 Hz.

    With PSK31 referenced to 100 Hz bandwidth and assuming JS8CALL uses the 2,800 BW of WJST-X, this makes JS8CALL look about 14 dB better. In other words, the difference between the two is not 6-(-24) = 30, but 30 - 14 = 16 dB. The formula is 10log(BW1/BW2). It should be noted that PSK31 is one of the poorest digital modes as far as performance.

    So if you're using PSK31 at 1000 watts, you'd need 25 watts.

    If we used the extra 30 WPM for Forward Error Correction (FEC), the difference would be reduced by another substantial margin. Maybe 10 dB? I didn't do the calculations. FEC is not my thing.

    Bottom line, there's no magic here.

    73,
    Chris, K9EQ
     
    N5RFX and AG5DB like this.
  2. W5LMM

    W5LMM Platinum Subscriber Platinum Subscriber QRZ Page

    You have absolutely no idea of my technical insight and experience. I've been networking and supporting computers and various operating systems for three decades.
    Wang, IBM, UNIX, Linux, OS/2 MACos, DOS3 and up, every version of Windows, all of it.
    Micro$oft has a bad habit of Beta-Testing their OS's on the paying consumer.
    To this day, windows 10 is buggy, features are suddenly removed or downgraded, software disappears, every update is a crapshoot as to whether mission-critical applications will continue working on the platform.
    Definitely NOT a good operating system to run in a production environment . AKA Garbage. Thanks for your "input"
     
    W1FVB and SP9BL like this.
  3. LA6VQ

    LA6VQ Platinum Subscriber Platinum Subscriber QRZ Page

    Just a small matter of precision (or nitpicking): According to the WSJT-X User Guide ยง 7.1, the reference bandwidth for FT8 is 2,500 Hz, i.e. 25X the PSK31 bandwidth in the article and 50X the FT8 bandwith (and then also the JS8CALL bandwidth). The difference between 2,500 and 2,800 Hz amounts to a mere 0.5 dB, so it is more than close enough for this discussion.

    With FT8 signals at the basis of JS8CALL, I guess they should be compared at identical bandwidths. Assuming even distribution of noise over the entire bandwidth, the 50 Hz bandwidth of JS8CALL and FT8 gives them a 17 dB noise advantage over 2,500 Hz bandwidth, while the referenced 100 Hz bandwidth of PSK31 would yield a 14 dB noise advantage over a 2,500 Hz bandwidth. Considering bandwidth alone, PSK31 should only be -3 dB compared to JS8CALL and FT8, but then we are not considering error correction in JS8CALL and FT8, nor the higher WPM, the free format and no need of time synchronization of PSK31. As you say, Chris, there is no magic, just adding more weight to some features at the cost of some other. All the modes are well thought out, making good use of the available computer capacity of their time. I guess it will be difficult to find a way to compare apples to apples, i.e. in a way that is fair to their various characteristics and primary uses. We may have to settle for comparing oranges to lemons or mandarin oranges, which, although they are close and related, will leave a touch of personal preferences in the (in)equation.

    73 Frode LA6VQ
     
    Last edited: Oct 18, 2018
    N5RFX likes this.
  4. NN2X

    NN2X XML Subscriber QRZ Page

    The magic is the following...There is no other digital coding scheme that can decode at -24dB below the noise floor, at 20wpm, while only occupying 50hz...

    That is the magic!
     
    LB9YH likes this.
  5. K5TRI

    K5TRI XML Subscriber QRZ Page

    With that impressive background of legacy technology, we'd love to have your feedback. If you could spare a few minutes, that would be great.

    https://insider.windows.com/en-us/how-to-feedback/

    73 Mike K5TRI

    p.s.: Yes, I work at Microsoft ;)
     
    KI5AIU likes this.
  6. W5LMM

    W5LMM Platinum Subscriber Platinum Subscriber QRZ Page

    Yes, I figured that one out immediately. As far as feedback, I've given more than my fair share of that, and feel as if it's fallen on deaf ears.

    We do agree on one thing though, When calling CQ DX, why must nearby people respond!?!?
     
  7. KY5U

    KY5U Ham Member QRZ Page

    All the monkeys sing....

    blob.jpg
     
    AC1IZ, KG5GCC and W3ATT like this.
  8. NN2X

    NN2X XML Subscriber QRZ Page

  9. SM0KIN

    SM0KIN QRZ Member

    If you like FT8 you'll love JS8
     
  10. W0PV

    W0PV Ham Member QRZ Page

    I always call "CQ RARE DX", that at least makes them think twice ... :rolleyes:
     
    KF4ZKU, KC2SIZ and W5LMM like this.
  11. K4SUE

    K4SUE Ham Member QRZ Page


    Latest (today's) tells a much different story
    Modes over last 2 hours
    Mode Count
    FT8 1153020
    CW 6016
    PSK31 2151
    JS8 1582
    JT65 1232
    SIM31 534
    MSK144 305
    PSK 186
    PSK63 88
    JT9 55
    OPERA 35
    ROS 34
    SSB 31

    25
    RTTY 17
    PI4 14
    MFSK16 5
    OLIVIA 5
    THOR 4
    PSK125 4
    OLIVIA-1 3
    DOMINO 1
    THOR22 1
    THOR4 1
    THRB 1
    SIM63 1
    CONTESTI 1
    OLIVIA-3 1
     
  12. NN2X

    NN2X XML Subscriber QRZ Page

    Imagine when the JS8CALL is actually released (Formally), Right now it is still on the pilot phase.

    Wait later today, JS8CALL increases, to 2nd place, but in any case, this mode, working at -24dB below the noise floor at 20wpm, will have an appeal, especially when it is officially launched

    I don't know of any other digital mode, that can make that claim (-24dB below the noise floor. , at 20wpm, using only 50hz of bandwidth), hence once this is released, it will grow exponentially.

    Cheers, NN2X, Tom
     
  13. K4SUE

    K4SUE Ham Member QRZ Page

    Well, I gave it a good test for some weeks and I think 20wpm is a hollow claim in my experience. Also, keep in mind, PSK Reporter count is based on CQs received by reporting stations, not total activity.
     
  14. NN2X

    NN2X XML Subscriber QRZ Page

    Which version of JS8CALL you have? The earlier versions (FT8CALL and I believe early JS8CALL), could only do 10wpm, so you might have an older version.

    The latest version can work at 20wpm...

    More choices at the end, and I predict there will be more enhancements, but what is smart about JS8CALL, it is similar to FT8. (But with a QSO)

    Best
    NN2X, Tom
     
  15. W4MHZ

    W4MHZ Ham Member QRZ Page

    Mama used to tell me if you are pointing your finger at someone three others are pointing back at you. ;):p:D
     
    KF4ZKU likes this.

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