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µwave Comm.

Discussion in 'Radio and Communications' started by Electroenthusiast, Dec 25, 2011.

  1. Electroenthusiast

    Electroenthusiast Member

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    First idea is pretty, but that just isn't practical because they have many cellphones in their home.

    No, i dont think i need an active repeater for this case, because the signal can be trapped clearly outside.
    '''legal problems''' - Is this because it can have high power?
    BTW, can i use same antennae for both wifi and cell phone signals(since they use same spectrum of freq)?
     
  2. 4pyros

    4pyros Well-Known Member Most Helpful Member

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    You can buy antennas and cables online. What frequency do you need?
     
  3. trash

    trash Member

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    No, active repeaters are actually quite low power.
    The real commercial units used by phone companies in places like shopping centres are about 5-10W.
    The kind used by farmers are only about 1W output. This doesn't sound like a lot but it is more than enough to cause problems in modern networks, especially in urban areas.

    Depending on where you live, either pyro or myself or somebody else might be able to tell you were you might find some antennas short of building your own.
    In Australia 800-920MHz is common for 3G and GSM. There is also an 1800MHz GSM and a 2100MHz 3G/4G.
    Some of our local telco shops and rural electronics shops sell suitable antennas.
     
  4. dave

    Dave New Member

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  5. Electroenthusiast

    Electroenthusiast Member

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    BTW, what are the major differences b/w active and passive repeaters? I suppose both require power to work, but active does amplification How they cause Network Problem?
    There are quite good ones available within 50$, i'll recommend him to buy one of that kind, seems to be worthy.

    @trash
    building one like that, i'll come back about this.
     
  6. 4pyros

    4pyros Well-Known Member Most Helpful Member

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    Last edited: Jan 21, 2012
  7. trash

    trash Member

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    Passive repeaters use no power. They are passive.

    Amplifiers have problems mainly because people don't install them correctly.
    The second is they sometimes feedback, oscillate, add noise and especially cause intermod.
    Sometimes the problems are noticed by the phone user but most of the time they are unaware they are causing a problem.

    The network operators can see trends in the network. If there is a rogue unit it doesn't take long to notice it.
    I do know one person who got caught out in just such a situation. Rather amusing who it was.

    Even when the carriers are testing their network, they know where their repeaters are and remotely shut them down before testing.
     
  8. trash

    trash Member

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    This is an example of a microwave beam bender. A passive repeater. The antennas are dishes connected with a piece of waveguide, but the same kind of thing works with UHF antennas and coax.

    http://aprs.fi/?lat=-33.0842&lng=149.6914&mt=roadmap&z=16&timerange=3600
    Use the street view and look east.

    This is a rather strange position for a beam bender. The distant station on one end is about 30km away. The other is only about 100 metres down the hill.
     
  9. Electroenthusiast

    Electroenthusiast Member

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    Amazing trash, how did you know this information, by experience? (i mean abt the 'problems they cause' and how/why - Any Links?).
    They track the repeater? What method they use to track the device?

    Edit:
    1. Good Information here - (6.7 MB)
    2. How to build Passive Repeaters
     
    Last edited: Jan 21, 2012
  10. trash

    trash Member

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    I've worked on mobile networks over the years.
    Part of that is installing and commissioning new base stations.
    So areas that I know that there are repeaters our test results can be crap.
    Repeaters that belong to our network we shut down before testing.
    We don't need to track them, they have often have a remote link that we can shut them down.

    I have a friend that installs repeaters for 3G in remote areas (not as part of the network) so we share information.

    The boss of the who is in charge of the network had a repeater running in it's house and it went faulty. He was rather surprised that a couple of his guys turned up personally at
    his front door. Rather embarrassing having to ask him if he had something running that might be causing problems.

    The group of people responsible for network integrity can see when a cell has problems.
    If it continues they send somebody out to investigate the base station. I doesn't take long to work out if the base is faulty or when we look at the incoming signals
    we can see the interference. At that point we set up RDF gear and go find the source.

    We're all pretty friendly about anybody causing problems because it's easier to get people to co-operate.
    If somebody is nasty etc, then he would have to call in the feds (ACMA) who can softly kick their door down. :)
    But we've never had to do that.

    You can look at ham radio "foxhunting" or "RDF" to see how hidden transmitters and interference is found.
     
  11. Electroenthusiast

    Electroenthusiast Member

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    great information there, but couldnt find much information about radio interference due to actve repeaters. Those repeaters only amplify incoming/outgoing waves, how would they cause interfernce. (Because, in my opinion those repeaters are not producing any freq which are out of desired spectrum. even if the filter is not accurate, the other spectrum is not used by cell phones/wifi).

    ham radios have now become extinct, i've never seen anybody using them nowadays.
     
  12. trash

    trash Member

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    These assumptions are really correct or relevant. There are several different issues here and a couple of different scenarios. It's very hard to understand the issues when you cannot see what goes on from the mobile phone network's point of view.
    I can tell you what to look for and read up on, but it probably won't make a lot of sense to you.
    But if you must this is some light reading on the subject of PIM (Passive InterMod) in WCDMA networks
    http://www.electro-tech-online.com/custompdfs/2012/01/Intermod.pdf


    Oh, they are going to tear you to pieces for saying that.

    I'm not sure how many hams there are in the USA, but there must be about half a million.
    I know there's about 2 million in Japan.
    In Australia numbers are increasing. There are probably about 20,000 hams here.
     
  13. davenn

    davenn Active Member

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    I get a posse together and prepare the lynch mob!!

    far out Electroenthusiast !!! you make some wildly inaccurate statements!!

    Dave <--- still a very active amateur radio operator after 30 years licenced
    VK2TDN
     
    Last edited: Jan 23, 2012
  14. JimB

    JimB Super Moderator Most Helpful Member

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    OK, can I join the posse?

    Having been interested in radio for about 50 years, and held my amateur licence since 1970, amateur radio in its various forms has provided a great hobby and support for various aspects of my professional career.

    Study some radio Electroenthusiast, and then you will be able to tell the difference between a mircowave and any other size of wave you care to mention.

    Jim GM3ZMA
     
  15. Electroenthusiast

    Electroenthusiast Member

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    Where was i wrong? Someone else was wrong, and it was not me. You can check the posts.

    @Dave:
    You can't call that inaccurate, it was my belief. Everyone here are not right always.
    BTW, i had an opinion that the no. has decreased, due to the advent of Internet.
     
  16. trash

    trash Member

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  17. 4pyros

    4pyros Well-Known Member Most Helpful Member

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    You did it again
    Hams will be the last to die.
     
  18. davenn

    davenn Active Member

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    unless we all give ourselves leukemia through over exposure to microwave RF energy hahaha

    As JimB said its a great hobby which has also helped me keep up with changing technology.
    speaking of which ... hey trash, me ol' mate ;) it must be time to get a bit more old cellphone site gear from your before it gets dumped haha


    checking the posts....
    Electroenthusiast, your quote...
    obviously your walk around with your eyes closed ;) we are definately alive, well and still kicking

    anyway have a look through some of the links that trash provided and I think you will find extinction is not in the near future.


    cheers
    Dave
     
  19. Electroenthusiast

    Electroenthusiast Member

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    End of it...
     
  20. trash

    trash Member

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    Yeah, I think that ship has sailed Dave.
    It's slim pickin's these days. Unless of course you've moved up to DIN connectors.
    If anything is going to the scrapys then I can usually bribe them with beer.
     
  21. Electroenthusiast

    Electroenthusiast Member

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    I was thinking about the Wifi radiations and the mobile radiations. Sources on the internet saw that the Wifi radiations are better than Mobile radiations when in context of human health. Don't know how this is possible. Aren't the radiation hazards depend on frequency? So the GHz wifi should be much hazardous than mobile radiations.

    Addin to this, the channels increases when the you increase the bandwidth in bitrates, which is again increase in frequency. Isn't this hazardous?
    As we know, the increase in frequency will deter the range of communication, whereas when you increase the bitrate, you are increasing the range of router. Little confused with all this, can anyone add up their understanding and discuss the same?
     

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