FCC Releases "symbol rate" NPRM

Discussion in 'Amplitude Modulation' started by K5UJ, Jul 29, 2016.

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  1. K4KYV

    K4KYV Premium Subscriber Volunteer Moderator QRZ Page

    What's the distinction between a facsimile signal and an analogue SSTV signal, other than the display medium used at the receiver? Wouldn't both be classified as "Image" as far as Part 97 is concerned?
     
  2. N2EY

    N2EY Premium Subscriber QRZ Page

    Yes.
     
  3. AC0OB

    AC0OB Platinum Subscriber Platinum Subscriber QRZ Page

    I must point out the following:

    97.3 Para. (3) addresses facsimile transmissions:

    "(3) Image. Facsimile and television emissions having designators with A, C, D, F, G, H, J or R as the first symbol; 1, 2 or 3 as the second symbol; C or F as the third symbol; and emissions having B as the first symbol; 7, 8 or 9 as the second symbol; W as the third symbol."


    http://life.itu.int/radioclub/rr/ap01.htm

    According to the ITU emission designators above and quoted in 97.3 (2), Data. Telemetry, telecommand and computer communications emissions are covered in (i, ii): specifically, "(ii) ...emission J2D and,... having an occupied bandwidth of 500 Hz or less when transmitted on an amateur service frequency below 30 MHz. Only a digital code of a type specifically authorized in this part may be transmitted."

    The designators in (ii) would cover these emissions:

    J2D: J - single sideband supressed carrier, 2 - single channel containing quantized information with the use of a modulating subcarrier. D - Data transmission, telemetry, telecommand.



    Phil
    --------------------------------------------------------------------
    AC0OB - A Place where Thermionic Emitters Rule!
    Besides, when you're a Ham, you experiment with and improve boat anchors - that's what you do!. [​IMG]





     
    Last edited: Sep 8, 2016
  4. W6RZ

    W6RZ Premium Subscriber QRZ Page

    It's definitely a gray area (no pun intended :)). It looks like some folks are exploring the distinction with narrow SSTV on 30 meters.

    http://www.wb9kmw.com/WB9KMW/tutorial/article_N-SSTV_30m.pdf

    Here's the link to FCC 06-149, where the transmission of 500 Hz facsimile in the RTTY, data portion of the band was added. Note that J2D (Pactor) was added later.

    https://apps.fcc.gov/edocs_public/attachmatch/FCC-06-149A1.pdf
     
  5. W6RZ

    W6RZ Premium Subscriber QRZ Page

    And what is your point exactly?
     
  6. K4KYV

    K4KYV Premium Subscriber Volunteer Moderator QRZ Page

    I would think that facsimile would be an image mode by definition, since like SSTV, fax is image modulation, not data modulation. Fax does not convert the text into characters as in the case of RTTY, but essentially scans a picture of the page and transmits it, just like SSTV. Furthermore, you can fax a photo, diagram or drawing just as easily as you can fax a paragraph of text. Likewise, SSTV would be indistinguishable from fax if you save the image and then print it; nearly all SSTV these days whether digital or analogue is accomplished with computers, not dedicated SSTV receivers. Remember the early Robot SSTV monitors that displayed the crude black & white image on about a 6"screen, line at a time, and by the time the last line of the picture was scanned, the first line had almost faded away?

    That's something that has always irritated me about ARRL. If your correspondence questions or includes any criticism or contradiction of their policy or opinion, they tend to simply not respond, IOW to stonewall.
     
  7. W6RZ

    W6RZ Premium Subscriber QRZ Page

    Before 2006, facsimile was an image mode only. But then someone petitioned the FCC to allow narrow facsimile modes (in particular Hellschriber), in the RTTY, data portion of the bands. So now facsimile is a data mode if it's less than 500 Hz wide, and an image mode if it's greater than 500 Hz wide.
     
  8. AC0OB

    AC0OB Platinum Subscriber Platinum Subscriber QRZ Page

    My point is that if one reads 97.3(2) literally, there is a 500 Hz bandwidth limit on data, telemetry, telecommand and computer communications below 30 MHz.

    I contend that a separate paragraph was written specifically for facsimile, 97.3(3), to distinguish it from data, telemetry, telecommand and computer communications, 97.3(2)(ii).


    Phil
    --------------------------------------------------------------------
    AC0OB - A Place where Thermionic Emitters Rule!
    Besides, when you're a Ham, you experiment with and improve boat anchors - that's what you do!. [​IMG]
     
    Last edited: Sep 9, 2016
  9. W6RZ

    W6RZ Premium Subscriber QRZ Page

    That's not how I read it. Perhaps some white space would help.

    *** start ***

    (2) Data. Telemetry, telecommand and computer communications emissions having

    (i) designators with A, C, D, F, G, H, J or R as the first symbol, 1 as the second symbol, and D as the third symbol.

    (ii) emission J2D.

    (iii) emissions A1C, F1C, F2C, J2C, and J3C having an occupied bandwidth of 500 Hz or less when transmitted on an amateur service frequency below 30 MHz.

    Only a digital code of a type specifically authorized in this part may be transmitted.

    *** end ***

    As I've said before, the 500 Hz limit only applies to A1C, F1C, F2C, J2C and J3C modes. Any mode ending in C is facsimile.

    For J2D (Pactor), there is no bandwidth limit. It is limited by the 300 baud rate rule in 97.307(f)(3). However, we know that OFDM renders the baud rate limit totally ineffective. We are already in an era of unlimited bandwidth. That's why removing the baud rate limit doesn't change anything except that single carrier modems can be used (which as posted by SM0AOM, is a more modern technology).

    This is why opposition to RM-11708 is silly. Of course, how folks feel about HF e-mail systems is a separate issue.
    But as I've said, that genie is out of the bottle, and can't be put back in.
     
  10. AC0OB

    AC0OB Platinum Subscriber Platinum Subscriber QRZ Page

    I think Mr. McVey summed things up very well in his submittal:

    https://ecfsapi.fcc.gov/file/109092726923452/McVey_Comments_RM11708RM.pdf

    I.E., give ARS OFDM transmission modes that require > 500Hz bandwidth's a separate sub-band (away from any phone slots) and produce an unambiguous list of SC's that have been fully defined in the public domain.


    Phil
    --------------------------------------------------------------------
    AC0OB - A Place where Thermionic Emitters Rule!
    Besides, when you're a Ham, you experiment with and improve boat anchors - that's what you do!. [​IMG]
     

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