RF Wastelands

This topic contains 5 replies, has 4 voices, and was last updated by  Alfredo_T 4 days, 5 hours ago.

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  • #41637

    Alfredo_T
    Participant

    Although I am not on board with the 45-50 MHz re-purposing proposal linked in the thread The Future (or lack there of) for AM Radio, I did notice an observation in that proposal that in New York City, a scanner can go for several days before detecting a carrier. That makes me wonder, what are some little-used segments of the radio spectrum, which could be monitored for days or longer before any signals were detected?

    So far, the ones that come to my mind are:

    • 90 – 110 kHz — formerly LORAN C
    • 1710 – 1800 kHz — formerly radionavigation
    • 42 – 50 MHz — formerly public service and unlicensed consumer products
    • 54 – 72 MHz — Formerly television channels 2-4
    #41639

    Andy Brown
    Participant

    54 – 72 MHz:

    http://bit.ly/2LqucVU

    1.71 – 1.8 MHz:

    Cochrane Technologies Broussard LA

    WNZG604 1.71084000 MHz. Active Exp. 2022
    WNZG605 1.71084000 MHz. Active Exp. 2022
    WPHW222 1.71584000 MHz. Active Exp. 2025

    County Of Hudson Jersey City, NJ

    WQFG689 1.71000000 MHz. Active Exp. 2026

    90 – 110 kHz:

    Boeing & Lockheed Martin still using 100 kHz

    http://www.mediaeng.com/specialprojects/90-110kHzp1.png
    http://www.mediaeng.com/specialprojects/90-110kHzp2.png

    42 – 50 MHz:

    10 pages of results with many still active

    http://www.mediaeng.com/specialprojects/42-50MHz.png

    Search results are not linkable in ULS like they are in the AM/FM/TV Query but you can rerun the searches by going to
    https://wireless2.fcc.gov/UlsApp/UlsSearch/searchAdvanced.jsp

    #41701

    SCOTUS9
    Spectator

    The Gray Spaces. 54 – 88 and 174 – 216 mHz.
    DoD uses them.
    NTIA wants them to extend rural wireless services.
    Some broadcasting companies want them back.

    #41704

    nosignalallnoise
    Participant

    42-50 MHz is still used for unlicenced consumer products but they’re not as widespread these days as they were 15-20 years ago. Still you can program the following frequencies into any scanner and drive around any good-sized city, especially around complexes and tenement blocks, and you’re liable to hear at least a couple voluntary domestic surveillance transmitters baby monitors (ahem ahem), usually barfing out dumbass amounts of RF. Some are way, way overpowered for what they are.

    49.300
    49.830
    49.845
    49.860
    49.875
    49.890
    49.895
    49.970

    You may need to deviate a few kHz from these frequencies to get a clear signal, depending how out of spec the transmitter you come across was when it left China. Scan around 45-46 and 49 and you might even hear some old grandmum who just won’t give up her 35-year old cordless phone for one of those fershluggin’ digital things all the young whippershnappers have.

    #41706

    Alfredo_T
    Participant

    I have a Zenith 7H820, which is a late 1940s vintage table radio that can receive both the original 42-50 MHz and 88-108 MHz FM bands. Years ago, I could occasionally hear a neighbor’s cordless phone, as well as some public service communications (possibly the Forestry Service). That radio needs to have capacitors replaced, as well as some other work, so I haven’t turned it on in a long time.

    I also have some 49.860 MHz crystals that were salvaged from toy walkie-talkies that would be fun to re-purpose. I just haven’t figured out what to do with them. There is a 49 MHz experimenters’ group online, but I do not think that they are very active.

    #41709

    Alfredo_T
    Participant

    According to the ARRL, 50.40 MHz is the AM voice frequency on 6 meters. If were to build a converter using one of those walkie-talkie crystals and a NE602, I could hear 6 meter AM traffic using an AM radio tuned to 540 kHz.

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