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Thread: mobile bug

  1. #1

    Default mobile bug

    i want to make mobile bug

    i found these lines which i am unable to understand ::

    ""The lead length of the disk capacitor is fixed as 18 mm with a spacing of 8 mm between the leads to get the desired frequency. ""

    you may check at
    http://www.electronicsforu.com/elect...e=Mobile%20Bug


    is these lines convey , that we have to adjust the spacing & lead length of capacitor
    HEY , i want to know is there any capacitor whose spacing & lead length can we adjusted

    if am wrong please me out.

  2. #2
    Senior Member Cyborg
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    Default

    lead length : means length of metalic wire attached to capacitor itself.
    8 mm between the leads : means these wire should solder on board contacts with drill hole 8mm apart.
    Nikhil Chandra | Bangalore

    Imagination is more important than knowledge.

  3. #3

    Default

    thanks for your help

    i want to know
    if we use a capacitor with 8mm ,4mm etc apart in board, is this make any difference in capacitor behavior

    what the use of drill them 8mm apart , as spacing of a capacitor is constant which is made during manufacturing
    then how can we change spacing

  4. #4
    Super Moderator T-1000 docel's Avatar
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    The .22 disc ceramic capacitor is used as a LC tuned circuit; with the leg lengths of 18mm spaced 8mm spacing and stray capacitance , it will act as a high gain tuned circuit at the Mobile phone transmitting frequency ( 900MHz - 3Ghz ).
    A 1nH inductor and a 1pf Capacitance will resonate at 3.55GHz. It will produce more Voltage (& current) at this frequency and may shunt or choke voltages @ other frequencies.

    The original authors' explanation of this ' acting like an antenna' is not correct as I see it. The antenna as such , is the part that extends from the top most part from C1 the 22pf Capacitor.
    any change in the given dimensions will detune the LC ratio and hence the Resonant frequency . This will lead to the circuits failure as it may 'ground' the signal instead of enhancing it.
    docel
    ^Anything is possible..
    after YOU prove it!!

    http://bangalorerobotics.tripod.com

  5. #5
    Senior Member T-1000 akshay66's Avatar
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    http://www.united77.com/projects.htm

    You can buy the kit here.
    Redefine it your way!!!!

  6. #6
    Super Moderator T-1000 docel's Avatar
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    Quote Originally Posted by akshay66 View Post
    http://www.united77.com/projects.htm

    You can buy the kit here.
    This guy is trying to MAKE it himself, for a change ......
    What good is a Ready-made link ?? It may discourage self learning and enterprise..... a foundation for the likes of Diwaker Vyas
    docel
    ^Anything is possible..
    after YOU prove it!!

    http://bangalorerobotics.tripod.com

  7. #7
    Senior Member T-1000 akshay66's Avatar
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    The kit will just provide him with components and circuit print out.He still has to make it himself.I know he'll learn more even in the process of finding components but i don't want him to leave this project just because of small component or doubt.The kit will atleast solve his capacitor problem
    Redefine it your way!!!!

  8. #8

    Default

    i understood, all concept you guys explained

    but i have still a doubt

    i want to know that, we have to use normal ceramic capacitor whose leg length is 18mm,and have to drill in pcb at 8mm apart

  9. #9
    Super Moderator T-1000 docel's Avatar
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    Youre right. Make sure the Capacitor is vertical.
    docel
    ^Anything is possible..
    after YOU prove it!!

    http://bangalorerobotics.tripod.com

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