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Is the HF Band a Noise Wasteland?

Discussion in 'Electronic Design' started by D from BC, Jan 26, 2008.

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  1. D from BC

    D from BC Guest

    I was reading on
    http://en.wikipedia.org/wiki/High_frequency

    The HF band is from 3Mhz to 30Mhz.
    (The upper f of AM radio is ~1.6Mhz)

    This band is used by CB radio operators and amateur radio operators.

    Anybody here just think:
    "Put the EMI here! It's ok." :p

    So some truckers get some static.
    HF Radio amateurs can use the internet.
    (Who wants to wait for sunspots to go away?)

    Has the HF band become the 'garbage dump' of the airwaves?


    D from BC
    British Columbia
    Canada.
     
  2. Bob

    Bob Guest

    CB uses the top end of HF. It is near useless during daylight hours
    for days at a time when the ionosphere is highly charged and
    signals from hundreds of miles away blot out the person a few
    miles away that you actually want to talk to. The unreliabilty
    makes it undesirable for radio communications of any importance.

    The radio hams and CB are on HF because back when the bands
    where allocated UHF was expensive and impractical due
    the limitations of the available technolody. No, nobdy thought
    "put the junk here", they made frequency allocations based on
    practicality.

    These days money seems to be the main driving factor.
    In Europe short range license-exempt digital-modulation
    walkie talkies are being allowed. I'v read they have
    about a 7dB advantage over FM. There is no technical
    reason to not allow full duplex operation or automatic
    frequency selection to minise clashing with other users.
    The cynic in me says that the billions the mobile phone
    companys paid for licenses has somthing to do with it.

    Bob

    Bob
     
  3. Jitt

    Jitt Guest

    Dont forget Shortwave broadcasts, and Land and Marine
    commercial SSB comms, military nets, time and weather
    signals...lots!
     
  4. Jamie

    Jamie Guest

    why would you want to wait for the sun spots to go away? it's
    better with them..
     
  5. John Larkin

    John Larkin Guest

    It always was. Stuff below 50 MHz gets reflected by the ionosphere, so
    at HF frequencies the whole world is in one noisy tin can. Natural
    atmospheric noise, lightning and such, is trapped too. That's why it's
    not worth designing an HF receiver with an especially good noise
    figure.

    John
     
  6. D from BC

    D from BC Guest

    I'm not familiar with sun spot effects on HF radio.
    I just thought.
    Sunspots>ionized particles>solar wind>trapped in earth mag
    field>charged particles in atmosphere>noise in HF band
    Plus some nice colours in the sky..

    Are you saying that during sun spots it's more uhhh...say
    'excusable'... to make EMI (radiated smps EMI) in the HF band?


    D from BC
    British Columbia
    Canada.
     
  7. mpm

    mpm Guest

    Thank god for noise blanker circuits....

    Speaking of spectrum wastelands.... the petition to reallocate TV
    Channel-6 to the FM band is back on the horizon. This time to include
    TV-5 as well. (USA)

    It would add substantially to the FM broadcast band, which is
    congested in most urban areas.
    And very few TV stations have elected 5/6 as their terrestrial DTV
    channel.
    Perhaps the time has finally come?

    -mpm
     
  8. John Larkin

    John Larkin Guest


    Do we need 15 more soft rock stations, or three more places to hear
    Prarie Home Companion?

    John
     
  9. Joerg

    Joerg Guest

    If you must live with small antennas you have to. One reason my EMC kit
    has a LNA.


    And we all by new car radios? Nah.
    Could use a few more country stations with the old stuff. And I want
    Wolfman Jack back!
     
  10. T

    T Guest

    The band is used by more than that. Yes we amateurs use from the 160m
    band up to the 2m band and then into the cm range. CB operators are
    strictly 11m which runs form 26.965MHz to 27.405MHz while the amateur
    10m runs 28.000MHz to 29.700MHz a whole 1.7MHz of bandwidth.

    Yes, we amateurs do use the internet, but we also use the radio.
     
  11. T

    T Guest

    Simple, the E layer of the atmosphere gets all charged up from that
    particle bombardment. That makes it reflect radio signals in the HF
    bands. You get increased distance.


    Now temperature inversions will duct VHF signals to distant locations.

    Get your amateur radio license. You might learn a thing or two.
     
  12. T

    T Guest

    No but we could use more community based stations and non Clear Channel
    stations.
     
  13. D from BC

    D from BC Guest

    Ahhh...
    So in that case.. I should have wrote:
    "Who wants to wait for lots of sunspots?"

    Amateur radio...psshhht :p
    'Can you hear me .zzshhhht..Can you hear
    me...zsshhhtt..what?.zsszzhhhst..Repeat that ,,,,zssshhhts'
    Bad enough I get that sort of frustration from my cellphone.


    D from BC
    British Columbia
    Canada.
     
  14. Joerg

    Joerg Guest

    Then one fine day there is a major power outage, the cell tower backups
    runs dry and everyone in the area finds zero bars on their cell phone.
    That is where point to point communication can save the day, and has
    many times.
     
  15. T

    T Guest

    Real amateurs use CW. That tends to get through static, plus we also use
    phonetics on the voice bands for those difficult to hear contacts.

    I will agree that cell phones sounds like sideband radio to me.
     
  16. T

    T Guest

    Exactly. There have been numerous instances where amateur radio has
    stepped in to save the day.

    Even now in the 21st century if your power goes out for more than 4 to 8
    hours you'll lose most cell service. Another 20 or so hours from that
    phone service goes.
     
  17. D from BC

    D from BC Guest

    More than that?
    I'm thinkn if the HF band is not used for emergencies, it can be
    buzzed with radiated smps noise.


    D from BC
    British Columbia
    Canada.
     
  18. D from BC

    D from BC Guest

    I think if anyone is serious about communication during a disaster,
    they would have a satellite phone (ex:Iridium Motorola 9505) and a
    solar charging system.
    Unfortunately that's >>$1000.00


    D from BC
    British Columbia
    Canada.
     
  19. Jamie

    Jamie Guest

    You old [email protected]!
     
  20. T

    T Guest

    Sure that might happen but you need to coordinate police and fire too.
     
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