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Thread: To reduce transmitter's range......

  1. #1
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    Default To reduce transmitter's range......

    hi techies,

    i want to reduce the range of a radio transmitter do i just simply reduce the length of the antenna? can i replace the antenna with just a piece of common wire? thanks for any help.

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    Default Re: To reduce transmitter's range......

    Quote Originally Posted by jacob View Post
    hi techies,

    i want to reduce the range of a radio transmitter do i just simply reduce the length of the antenna? can i replace the antenna with just a piece of common wire? thanks for any help.
    antenna length corresponds to wavelength.
    reduce antenna length hence will not change transmitter range.

    the medium (air) plays a big part to attenuate the signal and affects transmitting range.

    In labs, they put electrical shield (e.g. grounded mesh cage) at the boundry where you want the transmission to stop. Of course this is not easy at home.

    I put my BB Box in bedroom and for sure the signal is weak in the sitting room, since there is no direct unblocked path between box and sitting room.
    Last edited by ConnorMcLeod; 8th January 2009 at 12:47 PM.

  3. #3
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    Default Re: To reduce transmitter's range......

    perhaps the other thing you could try is to reduce the power of the transmission

  4. #4

    Default Re: To reduce transmitter's range......

    wat transmission (device) u wan to reduce?
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    Default Re: To reduce transmitter's range......

    Quote Originally Posted by jacob View Post
    hi techies,

    i want to reduce the range of a radio transmitter do i just simply reduce the length of the antenna? can i replace the antenna with just a piece of common wire? thanks for any help.
    You can possibly reduce the range. You can also possibly cause damage to the transmitter. You could also possibly cause radio interference since a changed antenna can radiate harmonics and parasitics that you may not even be aware of much more efficiently than the designated antenna.

    If you don't know what you're doing, don't do it. Note that many license-free RF devices are only approved for use in unmodified form; modifying them could get you into legal trouble.

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    Default Re: To reduce transmitter's range......

    Quote Originally Posted by CYRN View Post
    wat transmission (device) u wan to reduce?
    a video and audio transmission set.

    my set max range is 100ft. i wanted to reduce it by half.
    Last edited by jacob; 8th January 2009 at 08:45 PM.

  7. #7
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    Default Re: To reduce transmitter's range......

    Quote Originally Posted by jacob View Post
    a video and audio transmission set.

    my set max range is 100ft. i wanted to reduce it by half.
    If you have a removable antenna, you can insert a 6dB attenuator between the transmitter and the antenna. This assumes you're talking about free space propagation. For indoors, builtup, or otherwise obstructed environments it is extremely difficult to predict the range.

  8. #8
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    Default Re: To reduce transmitter's range......

    just cover the antenna with different thickness of materials, then choose the one you want?
    Sony Alpha 700 hobbyist

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    Default Re: To reduce transmitter's range......

    Quote Originally Posted by LittleWolf View Post
    If you have a removable antenna, you can insert a 6dB attenuator between the transmitter and the antenna. This assumes you're talking about free space propagation. For indoors, builtup, or otherwise obstructed environments it is extremely difficult to predict the range.
    sounds like a good solution. 6dB attenuator cuts the range by half right? can get it in simlim tower? any idea what's the typical cost?

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    Default Re: To reduce transmitter's range......

    Quote Originally Posted by zcf View Post
    just cover the antenna with different thickness of materials, then choose the one you want?
    what kind of materials?

  11. #11

    Default Re: To reduce transmitter's range......

    Quote Originally Posted by jacob View Post
    sounds like a good solution. 6dB attenuator cuts the range by half right? can get it in simlim tower? any idea what's the typical cost?
    6db cuts the transmission power by half... but it does not mean range is reduced proportionally.

    note the attenuating frequency.

    Littlewolf is rite in highlighting the diff between spec range and real world performance.
    Last edited by CYRN; 9th January 2009 at 11:51 AM.
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    Default Re: To reduce transmitter's range......

    Quote Originally Posted by CYRN View Post
    6db cuts the transmission power by half... but it does not mean range is reduced proportionally.

    note the attenuating frequency.

    Littlewolf is rite in highlighting the diff between spec range and real world performance.
    6dB cuts power down to 1/4. Effective range in a completely open environment is halved as power is inversely proportional to the square of the distance. But yah, in real world situations, things can be very different.

    Price depends on the type of connector and frequency of interest, you can get an idea here: http://singapore.rs-online.com/web/s...94857545&Nty=1 and here: http://sg.farnell.com/jsp/search/bro...ttenuator&Ntx=. I'm sure you can find them for cheaper in Sim Lim Tower though.

  13. #13

    Default Re: To reduce transmitter's range......

    oops... paiseh...

    forgetting wat I learned liao... 3db then is half power rite?

    heeheehee
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  14. #14

    Default Re: To reduce transmitter's range......

    Quote Originally Posted by jacob View Post
    hi techies,

    i want to reduce the range of a radio transmitter do i just simply reduce the length of the antenna? can i replace the antenna with just a piece of common wire? thanks for any help.
    Yes you can. You'll just be making it work less efficiently. But do note what LittleWolf mentioned that it might cause harmonics problems.
    Last edited by lsisaxon; 9th January 2009 at 05:06 PM.

  15. #15

    Default Re: To reduce transmitter's range......

    Quote Originally Posted by CYRN View Post
    6db cuts the transmission power by half... but it does not mean range is reduced proportionally.

    note the attenuating frequency.

    Littlewolf is rite in highlighting the diff between spec range and real world performance.
    For power, it's 3dB.

  16. #16

    Default Re: To reduce transmitter's range......

    Quote Originally Posted by jacob View Post
    a video and audio transmission set.

    my set max range is 100ft. i wanted to reduce it by half.
    Why would you want to do that? The range is determined by 1) the radiated power, as well as 2) the sensitivity of the receiver.

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    Default Re: To reduce transmitter's range......

    Quote Originally Posted by lsisaxon View Post
    Why would you want to do that?
    Beyond privacy reasons, it is only courteous (and good, in some cases mandatory practice) to use minimum necessary power (and thereby reduce interference/RF pollution). Same reason why one should adjust the volume of one's radio/TV set to a level where the neighbours are not forced to listen to it ...

  18. #18
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    Default Re: To reduce transmitter's range......

    Quote Originally Posted by LittleWolf View Post
    Beyond privacy reasons, it is only courteous (and good, in some cases mandatory practice) to use minimum necessary power (and thereby reduce interference/RF pollution). Same reason why one should adjust the volume of one's radio/TV set to a level where the neighbours are not forced to listen to it ...
    Ideally a transmitter and receiver should work in tandem and automatically determine the power to radiate. But I don't think such a feature would be common in mass market consumer devices... So they would just transmit at full power to ensure maximum coverage.

    But I guess the 802.11n standard allows for some level of directionality, not sure if this is something that's properly exploited to minimise the spread of the signal.

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    Default Re: To reduce transmitter's range......

    Quote Originally Posted by LittleWolf View Post
    Beyond privacy reasons, it is only courteous (and good, in some cases mandatory practice) to use minimum necessary power (and thereby reduce interference/RF pollution). Same reason why one should adjust the volume of one's radio/TV set to a level where the neighbours are not forced to listen to it ...
    that's right. that's the reason to reduce the range.

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