phone networks

Discussion in 'General Electronics Chat' started by MIRINGU, Jun 7, 2009.

  1. MIRINGU

    Thread Starter Active Member

    Mar 18, 2007
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    Hi, for a radio if the network is low we used to tie a long wire and put it outside,now what about for mobile phones if you are in low networked place .what can u do locally??
     
  2. Externet

    AAC Fanatic!

    Nov 29, 2005
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    Go to a higher level on a building, or climb a palm tree. Height is the equivalent of your radio long wire.
     
  3. MIRINGU

    Thread Starter Active Member

    Mar 18, 2007
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    Yes u can do this only when u want to call.but what do u do if u don't know when u be receiving a call?
     
  4. kubeek

    AAC Fanatic!

    Sep 20, 2005
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    Stay on the tree? :)
     
  5. franzschluter

    Active Member

    Jun 1, 2009
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    I am not too sure if higher grounds means better reception. This is only true for radio frequencies which utilizes sky wave propagation.. However mobile and GSM services utilizes multi path propagation typically on the microwave region which works differently. It can be that you get a better signal on top of a building.. But not on top of a tree that's located in a remote jungle is false and only a myth (Should be tested on myth buster). I once was in a province and had absolutely no signal on top of the coco nut tree. But out at see I had signal.. (Which is weird because in theory water is a source of propagation loss or something).

    http://www.geocities.com/gsmmobilereport/gsmradiolink.htm

    Best way to receive good signal is make a DIY antenna reflector. You can do this with a bunch of microwave foil. The DIY antenna for wireless routers will give you an idea how to help your signal. AM signal can travel along a wire.. FM only a little... GSM? No chance it will stick to the wire...In fact a long antenna will attenuate it or make it spread more. Microwave antennas are short.
     
  6. Wendy

    Moderator

    Mar 24, 2008
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    I like the idea of the reflector. Metal screen mesh, like what a screen door uses, would also work as a decent reflector.
     
  7. bertus

    Administrator

    Apr 5, 2008
    15,648
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    Hello,

    When you want to use a mesh as reflector for the GSM the mesh size must be less than 0.1 λ.
    The GSM works at 850, 900, 1800 or 1900 Mhz.
    The λ = 300 / 1900 = 15.7 cm, so the mesh should be smaller than 15.7 mm.

    Greetings,
    Bertus
     
  8. Wendy

    Moderator

    Mar 24, 2008
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    Most screen doors are around 0.1" (2.5mm) or so, so this should be no problem. I'm talking about something designed to block mosquitos and gnats. It also has lower wind loading too. The sweet spot for reception, if it works at all, will be very tiny.
     
  9. Externet

    AAC Fanatic!

    Nov 29, 2005
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    If that was right, cellular telephone companies would not look for high sites and spend on tall towers to install their antennas. Any ground level office/ warehouse would then work.:)
     
  10. Von

    Active Member

    Oct 29, 2008
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    Not all cell "sites" are on towers. It depends on the location. Many are on and IN buildings or structures. A tower is only used when the topography or coverage area dictates.
     
  11. franzschluter

    Active Member

    Jun 1, 2009
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    They place it on high sites depending on strategy. Hence the term multi path propagation is used in GSM. Since microwave signals love to bounce a lot before they reach their destination.. What they do is send them from strategic spots (not necessarily high). They just need enough height to make the signal bounce good at the ground.. They also install BTS inside buildings and even rooms because they want the signal to scatter as much as possible over a wide area indoors. This is not achievable if you do it from a very high place.

    The only reason they put it on top of high hills and buildings... Is because they have cell phone users are located at the top floor of buildings.. today there are nano bts stations that are as big as your fists and is used instead of a BTS station installed on the top of a building.
    See link of nano bts for reference..
    http://www.adc.com/productsandservices/wirelesssolutions/products/inbuilding/nanobts.jsp



    DIY antenna refelector
    http://www.instructables.com/id/Easy-wardriving-wireless-antenna-wifi-wlan/
    Try using these.... Some say it works also for gsm. Depends on which band you are operating at your current cell site IMO.


    Personal Fact:
    Even though I know it is ilegal (as a kid before 10 years ago).. I tried using my 5510 Nokia in an airplane. At ground there was signal... As the altitude climbed the signal got weaker and weaker.. At 100m signal was gone. (100m was only my assumption based on my eye sight).

    Cheers
    Franz
     
    Last edited: Jun 17, 2009
  12. Wendy

    Moderator

    Mar 24, 2008
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    I have to disagree with that statement, microwaves are line of sight, line of sight goes further higher. Basic RF theory. If you drive in the country you will see the towers are about 100' high.

    They are also directional, they don't waste any energy going up or down, just omnidirctional sideways.

    Modern cellphones are designed to be very low power, as opposed to analog phone signals. The idea is to switch between the cells as you move along.
     
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