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Radio Receiver w/o local oscillator

Discussion in 'Electronic Design' started by kolbep, Mar 26, 2009.

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  1. kolbep

    kolbep Guest


    I have seen this item on Ebay : Ramsey ABM1 Pssive Aircraft Airband
    Monitor Kit :

    Does anybody have a schematic, or an idea on how one of these operates
    (Without a LO).
    I find it a bit pricey (for a South African), so I would like to try
    build one of my own.

    I do quite a bit of electronics work, but have not had extensive
    experience with radio circuitry.

  2. 1PW

    1PW Guest

    Hello Peter:

    It could be a TRF receiver:


  3. TheM

    TheM Guest

    I think this is to allow you to listen to radio traffic while on board
    aircraft without interfering (there's no local oscillator).
    However, try explaining this to a stewardess or air sheriff; "Its not
    a superhet, lady, its just a passive detector with audio amp"....

  4. Andrew Holme

    Andrew Holme Guest

    His e-Bay listing gives the title of the patent abstract as "Aircraft band
    radio receiver which does not radiate interfering signals" - put that into
    Google Patents and you find US Pat. 5361405 filed Nov 30, 1990 for what is
    just a TRF receiver. How can you get a patent for that?
  5. James Arthur

    James Arthur Guest

    The patent is for
    a TRF receiver
    with the audio output tied to the antenna input through
    an earphone,
    a cap,
    and an inductor,

    if that makes you feel any better.

    James Arthur
  6. Guest

    Here are some examples:

    View profile Translated (View Original)
    More options Mar 26, 6:30 pm
    Date: Thu, 26 Mar 2009 15:30:29 -0700 (PDT)
    Local: Thurs, Mar 26 2009 6:30 pm
    Subject: Air Band
    Reply | Reply to author | Forward | Print | Individual message | Show
    original | Report this message | Find messages by this author
    there are lots of these on the net:

    be kind to your local pilots and avoid super-regens. Band Radio

    Usually a good Rf preamp and proper case design kills the LO leakage

  7. Sylvia Else

    Sylvia Else Guest

    They say they have a patent, and they do:

    It does look like a wideband TRF receiver. I don't know why they were
    granted a patent on it.

  8. Sylvia Else

    Sylvia Else Guest

    Could be. But if so, the patent examiner should be fired.

  9. Guest

    Go look at the job experience requirements for patent examiners, its
    disgusting. Many if not most of them have zero commercial experience.

    The ones I have delt with could not read the radiation pattern chart
    of a led, nor understand Snell's law. The initial application was
    denied because said examiner had granted a patent on another LED
    design that DIDN'T work and used it to shoot down ours.

    We got a commercial unit of the other design and put it on a
    goniometer and plotted the pattern, and it did not match the granted
    patent by a long shot. Software modeling proved it could not work. You
    must be wrong said the examiner. Then our lawyer hand carried a video
    of the tests to DC, and had a meeting with the examiner's supervisor.
    Amazing how fast that got cleared up, but costly. They still messed
    with the claims.

    Only problem is the patent with the bad engineering still stands
    and is still licensed, and the lame parts are in bulk commercial

    The wiki covers it here for the job requirements:

    Its sad and a national disgrace.

    Steve Roberts
  10. Sylvia Else

    Sylvia Else Guest

    The examiner is still supposed to apply the rules. It may not be his
    fault if he's been employed to do a job that he's incapable of, but he
    should still be fired.

  11. Greegor

    Greegor Guest

    Doesn't it work as advertised?

    Can a crystal radio be set up to monitor
    the entire aircraft band?
  12. krw

    krw Guest

    You aren't the only one to use that strategy successfully.
  13. krw

    krw Guest

    He may indeed argue until he's blue, but it takes his time every time
    he does. in the end, he's measured by income (i.e. patents granted),
    not office actions. You tend to get what you measure.
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