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Re: FM on the DX394?

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  • jchajecki
    ... I had noticed in the band plan that there were some frequencies allocated for FM mode, particularly on the 10m band. I also wondered whether FM mode was
    Message 1 of 7 , Feb 28, 2013
      > Very interesting question. I'm curious as to why you would like to add FM demod capability.

      I had noticed in the band plan that there were some frequencies allocated for FM mode, particularly on the 10m band. I also wondered whether FM mode was permitted - and used - on frequencies allocated to 'all modes' and wondered whether it would be worthwhile exploring them. I'm guessing they would have to be Narrow FM. If its not generally used and there is not much happening there, then it probably isn't worth the effort.
    • William Barrett
      At risk of being corrected... FCC doesn t administrate the bands by specific mode any more, but rather then by bandwidth of the transmitted signal. This was
      Message 2 of 7 , Feb 28, 2013
        At risk of being corrected...



        FCC doesn't administrate the bands by specific mode any more, but rather

        then by bandwidth of the transmitted signal. This was intended to encourage

        new modes be developed by leaving the door a bit wider than previously.



        Narrow FM is too wide for any of the bands below 28 mHz. NFM IS allowed

        on ten meters, but not even all of that band -- just the frequencies above
        29 mhz.

        Narrow FM as defined by FCC is wider than AM, which is why AM is allowed

        on the lower bands while narrow FM is not.



        There is a simplex at 29.600, and a series of repeater channels starting at
        29.62.



        There are a few other overlooked slivers other than the simplex and the
        repeater

        channels, but I've forgotten what they are. There aren't many, and activity
        on

        them must be near-zero would be my guess. If I recall correctly, narrow FM
        is

        allowed on any frequency above 29.3 mHz. That will cause some conflict from

        satellite downlinks, so, see the ARRL "Considerate Operator's Guide" for
        details

        on where narrow FM would be welcomed.



        Personally, I like ten meter FM a lot. It sounds lovely to the ear, and
        covers in

        two propagation modes -- near-in, via direct (but not classic "groundwave"),


        and DX via the ionosphere when it's open. Locally, the relatively longer
        wave

        compared to two meters provides good mobile coverage in a hilly area, the

        waves crawling down into the valleys better than two meters.



        See this ARRL page for more.

        http://www.arrl.org/files/file/conop.pdf



        and:

        http://www.arrl.org/bandwidth-faq



        and:

        http://www.arrl.org/band-plan





        bbT





        _____

        From: RADIOSHACKDX394@yahoogroups.com
        [mailto:RADIOSHACKDX394@yahoogroups.com] On Behalf Of jchajecki
        Sent: Thursday, February 28, 2013 11:31
        To: RADIOSHACKDX394@yahoogroups.com
        Subject: [RADIOSHACKDX394] Re: FM on the DX394?





        > Very interesting question. I'm curious as to why you would like to add FM
        demod capability.

        I had noticed in the band plan that there were some frequencies allocated
        for FM mode, particularly on the 10m band. I also wondered whether FM mode
        was permitted - and used - on frequencies allocated to 'all modes' and
        wondered whether it would be worthwhile exploring them. I'm guessing they
        would have to be Narrow FM. If its not generally used and there is not much
        happening there, then it probably isn't worth the effort.





        [Non-text portions of this message have been removed]
      • boblafrank
        http://www.bruhns.us/AM_vs_FM/Comparing_AM_and_NBFM.html
        Message 3 of 7 , Mar 1, 2013
        • Joe
          ... It is possible to receive FM with an AM receiver. It is called slope detection . When receiving FM signal turn the VFO slowly to the left or right of the
          Message 4 of 7 , Mar 13, 2013
            --- In RADIOSHACKDX394@yahoogroups.com, "jchajecki" <yahoog@...> wrote:
            >
            > Is it possible to add FM demodulation to the DX394?
            >
            > Couldn't see a mod for it anywhere. Just wondered if anyone had managed to do it?
            >

            It is possible to receive FM with an AM receiver. It is called
            "slope detection". When receiving FM signal turn the VFO slowly
            to the left or right of the signal and the audio will be intelligible.
            The audio quality will not be the best but quite enough considering
            the rare FM signals on HF. FM signals can be heard on 10 meters especially in the repeater section.

            HTH


            Joe
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