Device to Block a 0-20khz signal

Discussion in 'The Projects Forum' started by Ravenx30, Oct 25, 2016.

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  1. Ravenx30

    Thread Starter New Member

    Oct 25, 2016
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    Looking for a device to block/scramble/jam the low frequency range of 0-20khz also known as the hearing spectrum for a unI project. If not possible or too hard 1khz and below will do! Can't find any info ation online so came here looking for some advice?
     
  2. tcmtech

    Distinguished Member

    Nov 4, 2013
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    Put the receiver in a solid steel box lined with heavy foam. No RF or sound energy will reach it.

    Lack of proper information your part results in lack of proper answers on our part.
     
  3. MaxHeadRoom

    Expert

    Jul 18, 2013
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    Look up hi-pass filter, the basic is a R/C combo
    Max.
     
  4. crutschow

    Expert

    Mar 14, 2008
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    Depends upon how you define "block".
    How much attenuation do you want when it's blocked?
    How sharp is the cutoff you want between the signals passed and the signals blocked.
     
  5. jpanhalt

    Expert

    Jan 18, 2008
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    What frequency, if any, do you need to pass?
     
  6. Ravenx30

    Thread Starter New Member

    Oct 25, 2016
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    Hi guys firstly thanks for the responses! Essentially what I'm wanting to do is generate the block/jamming frequency in the air say a 5-10M radius. I read that there is a difference between jamming and scambling but Essentially after the method with the highest attenuation. I don't know where to start? Even if (if it's easier) 0-1000Hz. So say A was transmitting an number of frequencys within that range and B was the circuit generating the block. C (placed within the blocking frequancy) could not receive what A was broudcasting.
     
  7. jpanhalt

    Expert

    Jan 18, 2008
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    If you are in control of all of the TX and RX, a better way is to have a code for each receiver. Then when the TX only wants that RX to receive the communication, it sends the signal coded with that access code.

    John
     
  8. Ravenx30

    Thread Starter New Member

    Oct 25, 2016
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    Hi John that sounds complicated... not really bothered about having access at all just basically a scrambler/jammer bubble around the device shielding it from anything in the given range even if it just scrambles the signal without getting rid of it is enough.
     
  9. Ravenx30

    Thread Starter New Member

    Oct 25, 2016
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    Must be something simple to create a sort of bubble of noice cancilation within that range?
     
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  10. jpanhalt

    Expert

    Jan 18, 2008
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    I don't know what country you are in, but in most (perhaps all ) countries intentional interference with radio communication is very serious. The US generally will not arrest you and will simply tell you to stop, but not all countries are that understanding.

    You need to define what you want to do, and you must not interfere with others using the same frequency. Digital is the in thing today (and has been for awhile) and digital encoding is quite common place. I am not going to advise you how to interfer with radio communications, nor do I think anyoe on this site will help in that illegal endeavor.

    John
     
  11. Ravenx30

    Thread Starter New Member

    Oct 25, 2016
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    The range I'm looking at isn't banned in my country as no device I'm aware of runs at such a low spectrum which is why my university autherised it
     
  12. wayneh

    Expert

    Sep 9, 2010
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    What medium are we talking about, sound in air or electromagnetic EM radiation at that low frequency? It's too low to call RF, I think.
     
  13. jpanhalt

    Expert

    Jan 18, 2008
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    RF extends well into the "audible" range, but it is EMF, not pressure waves in air. Submarines use that range.

    The OP is completely vague (perhaps because s/h/i/t doesn't know about the difference between audible modulation of RF and transmission at those RF frequencies) about what frequencies will need to pass his filter. The question was asked, but not answered.

    John
     
  14. JohnInTX

    Moderator

    Jun 26, 2012
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    @Ravenx30
    There is some confusion here. Are you talking audio i.e. hearing sound pressure waves in the air generated by some electro-mechanical transducer or radio i.e. electromagnetic waves generated by antenna? These are two very different things. One topic is allowed. One isn't.
    Please clarify.
     
  15. Ravenx30

    Thread Starter New Member

    Oct 25, 2016
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    Im more after a kind of shield against electromagnetic waves ranging in that frequency if possible. such as creating a bubble of white noise to displace the frequencies or negate them.
     
  16. AnalogKid

    AAC Fanatic!

    Aug 1, 2013
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    Electromagnetic white noise will not "displace" or negate anything. It can appear to mask something by overpowering it beyond the ability of a receiver to discriminate, but out-shouting is not negating. Also, a minor point, there is no such thing as RF at 0 Hz (post #1).

    So, in a wild-assed attempt to be more precise, what is the source of the low frequency RF signal or radiation you want to cancel? Active noise cancellation, either acoustic or EM, is based on sampling the signal to be cancelled, generating an identical signal 180 degrees out of phase, combining the two signals within the propagation medium, and letting destructive interference do the cancellation. Are you saying that this is what you want to do, across *ten octaves*, in an uncontrolled circular or spherical space?

    ak
     
  17. KMoffett

    AAC Fanatic!

    Dec 19, 2007
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    Sound like Maxwell Smart's "cone of silence". ;)

    Ken
     
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  18. jpanhalt

    Expert

    Jan 18, 2008
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    This is still messing with usable and active RF frequencies.

    http://www.vlf.it/submarine/sbmarine.html
    http://www.vlf.it/itulist/itulist.htm

    The area was given as 10 miles. I am curious in what country this work is being done where it is not restricted or illegal to interfere with such communications. What is the purpose of creating such interference?

    A Faraday cage would not interfere and might accomplish the "bubble" you want, but one of that size would be quite an undertaking.

    John
     
  19. AnalogKid

    AAC Fanatic!

    Aug 1, 2013
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    Nope. a) That would be radius, not area; b) You have made an incorrect assumption about a nonsense statement.

    M is not a defined abbreviation for any base or derived unit of measure, according to SI. A unit abbreviation can be a capital letter only if the unit is a proper name, like Ampere or Henry. The older, CGS-based unit, the Maxwell, is recognized for legacy purposes and has the abbreviation M. m (lower case) is the abbreviation for meter (or metre), the base unit of length.

    Note that I'm not picking on you, j. The TS is consistently sloppy in his inconsistent descriptions.

    https://en.wikipedia.org/wiki/International_System_of_Units

    Attached is a summary guide for SI writing.

    ak
     
  20. jpanhalt

    Expert

    Jan 18, 2008
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    Who is worried about SI? Not me. I support the American way.

    Kinda of ironic that the attacchment you post uses a capitalized, non-SI unit:
    upload_2016-10-26_14-24-12.png
    Perhaps forther discussion on your tangent to nonsense should be referred to Professor Byte.

    Source:Wikipedia
    John
     
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