rf everywhere

Discussion in 'Misc Electronics' started by RichD, Mar 6, 2013.

  1. RichD

    Guest

    When you have several (sub)megawatt HF transmitters and a few
    directional antennas aimed on different continents, you really need a
    big switchyard. with coaxial relays. I do not understand, how to do
    this with open-wire systems.
     
    , Mar 15, 2013
    #21
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  2. RichD

    Tim Williams Guest

    Tim Williams, Mar 15, 2013
    #22
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  3. RichD

    Guest

    , Mar 16, 2013
    #23
  4. RichD

    Tim Williams Guest

    Oops, nix the trailing backslash.

    Tim
     
    Tim Williams, Mar 16, 2013
    #24
  5. RichD

    Fred Abse Guest

    The WWII, British, CH radar (circa 50MHz), used open wire feeders to the
    transmitting antennas. The transmitters were a Marconi-EMI television
    design, of a few hundred kW, modified for pulse modulation, one of the
    reasons for killing the early British TV service.

    The guy I knew who'd worked on it described how the routing at one site,
    around the edge of the field, with several corners, to conceal the feeders
    from the air, couldn't be made to work, and they had to go direct, making
    a beautiful sighting line to the camouflaged transmitter.
     
    Fred Abse, Mar 16, 2013
    #25
  6. RichD

    Guest

    Good grief, I didn't say open-wire was never used, just that it is
    more difficult.
    Perhaps Coax wasn't available? Seems like a perfect opportunity for a
    ruse. ;-)
     
    , Mar 17, 2013
    #26
  7. RichD

    Fred Abse Guest

    This was 1942 Britain.
     
    Fred Abse, Mar 17, 2013
    #27
  8. RichD

    Guest

    Duh, really? <boggle>
     
    , Mar 17, 2013
    #28
  9. Well, a lot of it is. THAT antenna array Is still there, however.
    No, it isn't. it isn't even a Frisbee golf course.

    That particular array is one of the only remaining historical elements
    of the site. It is now a learning center for radio broadcasting.
    And your alzheimer's set in in the mid '90s.

    And some was done by hand on that array in the picture.
    3 transmitters were replaced.
    Original footprint.
    Never happened.

    VOA BBC still exists.
     
    DecadentLinuxUserNumeroUno, Mar 24, 2013
    #29
  10.  
    Cydrome Leader, Mar 25, 2013
    #30
  11. RichD

    josephkk Guest

    Once upon a time i had a USC-30, 2 to 30 MHz 1kW transceiver, in my care.
    It auto-tuned in the same way. I got to watch it once (with the covers
    off) and it was a thing of beauty to behold. It had its own low power (50
    W) dummy load and tuned up into that. Then it commanded the auto-tuner
    of the selected antenna to tune up. Just beautiful, but 30 seconds for
    any frequency change from 100 Hz to 28 Mhz. You used a different receiver
    and antenna to find an empty spot in an authorized band to transmit.

    ?-)
     
    josephkk, Mar 28, 2013
    #31
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