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Thread: 10 Meter band plan question

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  1. #1
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    Default 10 Meter band plan question

    There was wonderful sporadic-E condx tonight here in Florida. However I have a question. Is it OK to use the area between 29.200 and 29.300 for FM simplex? 29.600 of course is the FM simplex calling frequency, but since it is surrounded by 10 Meter FM repeater input and output frequencies, where is one supposed to QSY once that frequency becomes busy to continue a QSO?

    I went to 29.250 which from what I am understanding is OK due to the ARRL band plan. http://www.arrl.org/band-plan-1

    Am I interpreting this correctly, as the area between 29.200 and 29.300 does not seem to be allocated for anything? I really enjoy 10 Meter AM, but must confess that 10 Meter FM simplex was a lot of fun for a change, with several stations being 5/9+ with full quieting! Thanks in advance for replies.

  2. #2

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    FM is allowed on all amateur radio frequencies where phone operation is allowed EXCEPT for the 60-meter band. The only stipulation is that on frequencies below 29.000 MHz the modulation index cannot exceed 1.

    Considering that the ARRL doesn't even follow their own "band plan" . . .

    The frequency 29.300 MHz is widely used in Asia, and somewhat in Europe and Africa, just like 29.600 MHz in North and South America.

    You will find VERY little FM operation below 29.300 MHz unless you, and another station, delibertly decide on the frequency.

    The only slight problem that you might have in the 29.400 MHz to 29.500 MHz segment is the downlink from OSCAR VII (AO-7) when it is operating in Mode A.

    Glen, K9STH

  3. #3
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    Quote Originally Posted by K9STH View Post
    FM is allowed on all amateur radio frequencies where phone operation is allowed EXCEPT for the 60-meter band. The only stipulation is that on frequencies below 29.000 MHz the modulation index cannot exceed 1.
    Glen:

    I have heard that mentioned before. How does one determine their FM modulation index? On HF FM, I use a Kenwood TS-950SDX, and I do not see the FM modulation index mentioned anywhere in the owner's manual. The FM mode on the rig only has one setting, so there is not a narrow or wide setting.

  4. #4
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    Default

    --Yeah, it would be "neat" to use FM on HF bands, but I have no idea if my Yaesu FT-857D will do it (at work and don't have manual here). As long as it took up no more bandwidth than a traditional AM signal, it would be fun. Not sure what modern rigs are actually capable of a modulation index of less than 1. I'm not sure if "FM-N" (FM Narrow) that are in many HF rigs, has a modulation index of less than 1.
    Adam
    K5AHH

    We make a living by what we get, we make a life by what we give. --Sir Winston Churchill

  5. #5

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    4B:

    Modulation index is defined as the absolute value of the deviation divided by the highest modulation frequency. For example, "normal" deviation in North America is +/- 5 kHz and the highest modulation frequency utilized by the vast majority of transceivers is 3 kHz (3000 Hz). Dividing 5 by 3 you get a modulation index of 1.6667. To achieve a modulation index not exceeding 1 would mean that the deviation cannot exceed +/- 3 kHz.

    Most of the "modern" transceivers with HF FM capability have a "narrow" deviation position which limits the deviation to +/- 2.5 kHz which produces a modulation index of 0.8333 which, of course, is less than 1 and is therefore completely legal below 29.000 MHz.

    If the transmitter does not have a +/- 2.5 kHz deviation setting (only has +/- 5 kHz deviation) then it is NOT legal to use below 29.000 MHz.


    AHH:

    See above. The "FM-N" on "modern" HF transceivers equates to +/- 2.5 kHz deviation and is therefore legal.


    By the way, FM and PM (phase modulation which most of the older commercial "FM" units actually use) are called "angle modulation" and that is the reference in 47 CFR Part 97.

    Glen, K9STH

  6. #6
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    Excellent explanation Glen, thank you! My initial post was out of concern to not QRM areas of 10 Meters that is not "designated" for FM simplex use per band plan. The input/output frequencies of 10 Meter repeaters is obvious. I suppose 10 Meter sattilite activity is very limited as you responded, so the area below 29.500 seems most appropriate. Thanks again.

  7. #7
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    K5AHH



    On an FT-857/897D

    Press "function F" button for a fraction of a second...
    Scroll to menu MFm.
    Menu MFm...the "C" button sets the deviation to NARROW (NAR)
    The radio must be in FM mode for the menu selection to be valid.

    The mode indicator (Top line of the display, to the right of the VFO indicator)
    will change from "FM" to "FMN" to indicate FM Narrow band operation.

    Page 16 of the FT-897D manual, bottom section.

    The above descriptions are valid on an FT-897D.
    Last edited by KB3LIX; 06-02-2011 at 07:29 PM.

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