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Wideband Transmitter Design

Discussion in 'General Electronics' started by Victor Vector, Oct 29, 2003.

  1. With the proliferation of wireless technologies and the soon to be
    implemented RFID technology I was prompted to think of a way of
    disrupting the flow of these communications over the airwaves.
    possible uses could be jamming cell phones in cinemas or jamming WiFi
    in starbucks and watching the buisnessmen cry cause they cant get
    their e-mail. Thus I propose the idea of a wideband RF transmitter
    capable of producing noise on a variety of frequencies and that is
    also portable/breifcase sized so as you dont attract too much
    attension. Is a spark gap, the most simplest of transmitters the way
    to go. Does anyone still know how to build a spark gap and are they at
    all tuneable and how do you boost the output so as cellular and WIFI
    can be drowned out, Thanks for any ideas on this subjdect
     
  2. John Larkin

    John Larkin Guest


    Why not just throw a brick through the window of the nearest police
    station?

    John
     
  3. Dave VanHorn

    Dave VanHorn Guest

    :>Thanks for any ideas on this subjdect

    Dont.
     
  4. Jimmy

    Jimmy Guest

    I built an FM transmitter that constantly scans the FM broadcst band and
    locks on a particular freq when a microphone located outside my car picks up
    the 1000hz tone broadcat by the transmitter. Pressing a button generates a
    single sweep of the band and goes practically unnoticed by nearby listeners
    who happen to hear it on the radio. Only if the radio receiver is putting
    out a couple hundred watts will I get a lock. You can imagine how much fun
    this can be. Only problem I have with it is that few people who have these
    loud stereoes in their car listen to FM but I do catch a few.
     
  5. I'm extremely glad you don't know shit from apple butter
    about electronics. If you did, you'd start with Marconi's
    sparkgap XMTR and go from there.

    Then, you'd spend ten to twenty years in jail.

    Mark L. Fergerson
     
  6. A sparkgap's a terrifically effective gadget for wiping out AM over a
    very broad band indeed, but with most comms now operating in other
    modes, it's far less effective, I'm afraid. Aircraft comms are still
    AM, though and since you're line-of-sight with them, you might bring a
    few planes down even if you can't screw up Starbucks' muzac.
     
  7. No he won't, aircraft operators have very elaborate com failure procedures.
    OTOH, he will have the FCC and the FAA at his doorstep in no time. Which
    is in turn what he will have to serve.

    Michael
     
  8. default

    default Guest

    A spark gap is not the best idea for a jammer. They are inefficient.
    Somewhat audibly noisy also - presumably you'd want to be
    surreptitious in your activity . . . Also you run the risk of
    interrupting more than the person you find offensive.

    I like the idea I saw on the web. The guy used the final amplifier
    and exciter from a junk cell phone and a sweep generator to rapidly
    switch frequencies. The people that built them claimed they worked
    well for local disruption in shopping malls, restaurants, and on the
    road.

    Professional/commercial cell jamming devices probably use the same
    scheme. See http://www.monix.com.tw/mgb1.htm or
    http://www3.sympatico.ca/ChanLiYen/Cordless/list.htm

    Use Google to search the newsgroups
    http://groups.google.com/advanced_group_search Search on the phrase
    "cell phone jammer" and or "cell phone" +jammer
    the schematic I saw may still be up and about somewhere (I know I
    copied it).

    From the newsgroups search I just ran:
    I don't know if it works or not, but with all new parts it won't set
    you back more than $20 or so.
     
  9. Jim Thompson

    Jim Thompson Guest

    Complaint sent to Google with copies to FBI and FCC ;-)

    ...Jim Thompson
     
  10. Quite true. A competently imaginative neoLuddite asshole
    would look at Marconi's loop and think about slide
    trombones. Getting it to slide fast enough to bugger
    FM/PM/PWM/ agile comms will be, um, difficult unless he
    considers altering its length electrically, switching
    through a series of loops (a la "multiwave" antennae), or
    something like that. Hell, I thought that up thirty years
    ago (but didn't try it).

    I hope he enjoys buggering (or rather being buggered). If
    he's successful, he'll get plenty, especially if he follows
    any of the hints he gets here, so keep 'em coming!

    Mark L. Fergerson
     
  11. default

    default Guest

  12. I Love It! I need it!! When can you ship me one!!
    Glenn
     
  13. Dennis Davis

    Dennis Davis Guest

    jimmy,you're a dick lol, go find a church somewhere and bother them
    instead,what an idiot
     
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