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µwave Comm.

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

  1. 4pyros

    4pyros Well-Known Member Most Helpful Member

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    You realy can't tell without a computer. You would have to comunicat with the hotspot to tell. The keypob is a recever only. It has no transmiter for communicashoin. You can find signals with the keypob and then test with your computer.
     
    Last edited: Jan 7, 2012
  2. Electroenthusiast

    Electroenthusiast Member

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    Yes, i understood that.
     
  3. davenn

    davenn Active Member

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    You have a VERY strange view of RF and microwaves mate ;)
    time for you to do some reading I think ;)

    There is NO difference between RF and Microwaves .... Microwaves ARE RF!!! just really high freq RF. As Nigel said the uWave bands are generally considered to start at 1GHz
    The RF spectrum exists from ELF Extra Low Freq a few kHz they use for submarine comms right through to many 100's of TeraHz up to before we hit IR and Visible Light.
    Its ALL RF regardless of if it is low freq or UHF or microwave bands in the GHz or THZ

    Dave
     
    Last edited: Jan 9, 2012
  4. dave

    Dave New Member

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  5. davenn

    davenn Active Member

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    Any reduction in cost would be because of the smaller physical size of components and circuit board would be much more compact
    when using the 2.4 and 5.7 GHz freqs.
    With tranceiver gear I have built on those and higher freqs, 10GHz and 24GHz, They lend themselves to much more compact circuitry.
    example the higher you go in freq the physically smaller inductors MUST be.

    cheers
    Dave
     
  6. 4pyros

    4pyros Well-Known Member Most Helpful Member

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    The antennas are smaller two and can be made "on board"
     
  7. davenn

    davenn Active Member

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    yup another great reason to add to the list :)

    D
     
  8. trash

    trash Member

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    Sorry electro, I haven't logged in for a while. Busy post xmas period.

    Difference between a microwave oven's signal compared to those of communications.
    Well the first is power. Microwaves are obviously designed to heat material, so they are high power.
    Communications systems in S band are typically low power. Less than 1 watt. The exceptions are for broadcast applications, and even then these are low power compared to microwave ovens. MATV systems are ~100W. Most mircowave ovens are >500W.

    The second is modulation. Microwave ovens aren't modulated. They're just a big fat carrier.
    Communications systems are modulated. Either narrowband AM/FM/SSB, or wide band TV,QAM,COFDM etc.
    A microwave oven's magnetron is really nothing but a big diode. Or one might even say that it's a microwave lightbulb.
    It's a brute force crude device. The oscillator is the output.
    Communications oscillators are low level. They may be directly modulated, or they may be mixed with other signals at low level.
    This modulated signal is then amplified before being transmitted. Quite often that amplification needs to be linear, though not always.

    But the big difference is in stability and phase noise.
    When a microwave turns on, it drifts down the the band as it warms up. Even if we look closely at the carrier on a spectrum analyser it's a rather dirty kind of signal. It really is a lot like a lightbulb with respect to frequency. Consider it in terms of a red light bulb. (painted or otherwise) It emits red light. This seems straight forward but the red light from a light bulb is many colours of red.
    A communications oscillator is one of high stability and low phase noise. It's more like a laser in terms of light. Think of a red HeNe laser. This is a red laser, but it is only one colour of red. It's narrow band and it's frequency and phase are very stable.

    It's not really a function of frequency. It's just a function of mass production.

    Google is also your friend. Try "Wardriving".

    These are probably nothing special and it's just a marketing tactic. "Our containers are special. We've made them especially for use in microwave ovens."
     
    Last edited: Jan 15, 2012
  9. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    You would be wrong, some plastic containers absorb microwaves, so get hot (and soft) if you put them in a microwave oven. I've seen, and owned, a number of plastic containers over the years that are no good in a microwave.

    If it was just a marketing tactic then ALL plastic containers would say it :D
     
  10. trash

    trash Member

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    I can see your an engineer and not in the marketing department.
    If all products said the same thing, then that wouldn't be very good marketing.
    Marketing has nothing to do with the truth. It has everything to do with sales.

    Engineering on the other had is based on truth, well that's generally the rule.
    But you cannot engineer out stupidity. I have a "microwave safe" (the local marketing term)
    plastic container. It does pretty much what you have described when I push it past it's engineered limit. I've warped the shape to use it as a waterproof project box. The circuit board which was slightly larger than the box now fits.

    Now this isn't to say that some companies might use higher temperature plastics to do exactly what you say. After all, some people do the right thing and are honest.
    But this isn't the perfect world and when an offshore company is not accountable for their marketing, then if they save 10 cents on 10 million units, that's $1 million dollars more profit for a product which most people are not going to notice the difference.
     
  11. Electroenthusiast

    Electroenthusiast Member

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    @ trash

    Thanks for the reply... you might be late, but you got me good piece of information.
    BTW, in some movie... they used to test presence of a target using a microwave oven. There they used radar to cook food inside the oven. That was to create some fun.

    Another ques related to Microwaves: In one of my friend's home, i/we cannot receive any mobile(microwaves) signal inside the home. To receive/make calls, i need to get-out of the building and use it in backyard/outside portico. Even we can't access wi-fi signals from the next building. Do you have any idea to sort out this problem? I'm wandering with an idea.
     
  12. 4pyros

    4pyros Well-Known Member Most Helpful Member

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    Metal building blocking signal, or florescent light interfering with the signal.
     
  13. Electroenthusiast

    Electroenthusiast Member

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    Hmmm... But i've seen many good(metal building block) buildings around with no such probs. No florescent light interference, because it happens (also) without the light switched ON. Even then, they emit IR and i have a notion that it causes no interference with mobiles/wifi.
     
  14. 4pyros

    4pyros Well-Known Member Most Helpful Member

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    I was just guessing. Ether something is blocking the signal or something is interfering with it. You tell me!
     
  15. trash

    trash Member

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    It depends on the building and the source of the signal.
    Here it is not uncommon for 1800MHz or 2100MHz 3G to have problems indoors.
    2.4GHz with low signal strengths, no surprised there either.

    It is most likely that the building is just of good solid build. There isn't a lot you can do about it.

    Shopping centres are also another place that have similar problems. They have a distributed antenna system either via a repeater or their own base station in the building.

    In your case, moving closer to a window is about the only option. Passive or active repeaters are an option for each service but this isn't a simple as just moving close to a window or ran coax outside and use the correct antenna for the task required.
     
  16. Electroenthusiast

    Electroenthusiast Member

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    Maybe, it's a 3 storey building, off course a good quality, strong building. And the buildings next to it is 2 storey, and very much open in the backyard.

    Maybe the signal source abides all standards(= power of signal emitted).
    How about using a mirror/ something like that?
    Antennae / Repeaters??? That's interesting... what kind of repeater should they use.
     
  17. trash

    trash Member

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    Ok, well lets start from the bottom.
    What is it you're trying to do ?
    ie. a 2.4GHz Wifi link from my friends place next door to my computer etc.

    The distance, powers, types of equipment and antennas etc.

    Repeaters exist for a number of services, even cell phones and wifi.
    But each situation needs careful consideration. Active repeaters can cause more problems than you bargain for.

    On some other forums it is just easier to ask people just to tell the thread exactly what they want to do.
    We don't care about legalities, we solve the problem and then the person asking the questions can worry about how they want to deal with the solution.
     
  18. Electroenthusiast

    Electroenthusiast Member

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    Yes, i wanna direct all the mobile signals, that which i can catch outside the building.
    What type of repeaters/antennas are they? Wifi is not in priority.
     
  19. 4pyros

    4pyros Well-Known Member Most Helpful Member

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    You can try passive repeaters.
    Just two antennas tuned to the right frequency. One inside and one outside connected by a wire.
     
  20. trash

    trash Member

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    Ok, well there is an order of doing things.

    The first is to get an external antenna. Either a car kit antenna or something like a yagi or if you can't find one then either making a yagi or a double diamond antenna.
    Run this inside to your mobile phone. Having your phone sitting in a car kit in your house lets you use it hands free with good coverage and keep the phone charged.

    If this isn't practical, then the next step is the passive repeater like pyro has suggested.
    It's best to use a high gain external antenna and a short run of coax to the internal antenna which is something like a small omni.
    I have a friend who lives out on a farm on the fringe of coverage. He can make a call if he's outside the shed, but inside there just wasn't enough signal.
    A home made yagi on the roof with the coax connected to a bulk head connector he had drilled into the roof. On the inside it was just a short (1/4) length of brasing rod soldered to the bulkhead and the roof acted as the (inverted) ground plane. It worked a treat. I even took my spec-an out there one afternoon and pointed my RFI antenna at it and there was clearly a reasonable signal coming from it, about 10dB over what was coming through the open door of the shed.

    In the worst cases then you can consider the active repeaters. Which are not legal in a lot of places. Though here in Australia it doesn't stop a lot of people installing and using them. Occasionally they cause a problem and then people like me are sent out to find them and on some occasions talk nicely to the offenders.
    They do sometimes cause problems to mobile networks but at the same time they do work quite well. They're the option of last resort and they require some knowledge to set them up properly. They work best in very remote areas, not in suburban areas.
     
  21. Electroenthusiast

    Electroenthusiast Member

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    That would be good. In this case, i think, there is no need to worry about the power output from inside antennae(no need of spectrum-analyser). Any circuit to give me an idea?/Can i buy it for somewhere.
     

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