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Get the frequency of the signals around you

Discussion in 'Electronic Design' started by butthead, Oct 8, 2003.

  1. butthead

    butthead Guest

    Hi,
    I would like to build a device that would detect via an antenna a
    certain range of frequencies (may it be RF, ultrasounds, sonar..) and
    give the value.
     
  2. Ken Taylor

    Ken Taylor Guest

    Look up 'spectrum analyzer'.

    Ken
     
  3. Ben Pope

    Ben Pope Guest

    Well for a start you need to define your signal type.

    RF is an electromagnetic signal.

    Ultrasound and sonar or longitudinal pressure waves.

    Two VERY different things.

    An idea of the frequency range is useful too. For example most people can
    pick up electromagnetic radiation of 430-750THz and classify that pretty
    well with their eyes.

    You'll need different techniques for different frequency ranges.

    Ben
     
  4. Active8

    Active8 Guest

    have fun. you're looking at $100 or so just to build the front-end and
    1st mixer using Mini-Circuits or MaComm parts. Optoelectronics used to
    make a snooper that would do this for you, but it's classified as a
    nearfield detector and they may have been forced to stop selling them to
    the general public because it blows the cover of the cops and they can't
    handle hand signals like soldiers.

    mike
     
  5. N. Thornton

    N. Thornton Guest

    Hi. I have detected the signals around you. I can safely say 99% of
    them are of no value at all. Some of the rest are of great value.

    Regards, NT
     
  6. butthead

    butthead Guest

    Hi,
    I know that these waves are different but i don't mind the range. I
    mean wether it is to pick up RF frequencies or to pick frequencies
    emitted by a remote control...
    I just wanna get an idea
     
  7. Ben Pope

    Ben Pope Guest

    Well they're both EM radiation, but obviously at significantly different
    frequencies.

    So you want to know specific frequencies in a narrow band or rough
    frequencies in a very wide band?

    You'd like a meter that says you currently have lots of RF on the FM band,
    and somebody is pointing a remote control at you, and the micowave in the
    kitchen is currently on. But nobody is using their mobile phone in the
    vacinity.

    That type of thing?

    Ben
     
  8. Active8

    Active8 Guest

    but he said around *you*, not *him*. :)

    i'm currently receiving signals around me but i'm not *get*ting them.

    brs,
    mike
     
  9. Newsie? Is that you?
     
  10. "Nearfield detector" eh? Sounds like a very useful piece of test
    equipment for the radio amateur who likes to build his own stuff.
    Check for out-of-band emissions, harmonic radiation and so forth. Are
    they widely available outside of the US?
     
  11. But surely this device is just a cheap 'n' chearful type of spectrum
    analyser, isn't it? How can they ban the sale of SAs?
     
  12. Active8

    Active8 Guest

    most likely.

    the rumor(?) of the ban had do do with the fact that it's sort of a
    surveillance device. if you lived in the woods, you wouldn't expect a
    near field signal from say a cop car. since the cops are too lame to
    observe radio silence... in the city, you would know what was normal and
    a sudden near field emmision in the cop band would alert you.

    i don't know if you can get one. goto the Optoelectronics website. i
    forget what it was called. the description says it all. the BW is
    enormous.

    but i wouldn't use it as a lab tool for emmisions. it's not going to
    tell you how many dB down your harmonics and spurs are. just filter your
    bot controller real good and get a HAM to help check emmisions if you're
    worried.

    it does (did) log signal freqs received into memory and i think it had a
    vibrate mode to alert you to a nearfield emmision.

    mike

    BTW. i got one of their $350, most excellent freq counters. it arrived
    in a box emblazoned with "made in the USA" or "proudly made...". the
    damn thing didn't work. impatient, i opened it and the solder on the
    surface mounted hold switch looked suspect. a wiggle pulled the switch
    off the board. immediate problem solved - they won't count on hold. poss
    long term prob... bad QC.
     
  13. maxfoo

    maxfoo Guest

    Do a google search for "grid dip meter".
     
  14. Most of 'em are deaf as a post. One assumes the OP wants a reasonable
    amount of sensitivity.
     
  15. maxfoo

    maxfoo Guest

    Do you know what they same about assume?
     
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