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Broadcasting FM at home ?

  1. May 1, 2008 #1

    JPC

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    Hi

    I usualy lissen to radios on internet, and i would like to be able to hear it everywhere in my house, rather than just when i am on my pc.

    Does this exist : a Frequency Modulator that i can plug by USB to my pc, and broadcast localy (like a 250 meters range) my internet radio or any music files from my PC ? Where i can set it to unused Frequency intervals.

    If yes, can you please give me the specific name so that i can search in Amazon or other websites
     
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  3. May 1, 2008 #2

    BobG

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    I don't know if anyone sells them, but I'd almost be surprised if no one did.

    You can buy an RF mouse that transmits at low power and the USB receives it. An FM transmitter that could be received on any radio on the house would be the same in principle, although there are a few things that would have to be taken into account.

    If you're transmitting in the FM band, the power has to be low enough that you're not interfering with the neighbors radio. That puts a damper on someone manufacturing an FM transmitter not knowing whether it will be used in a 20 room house or a single room dormitory room.

    Using a different frequency, especially a spread spectrum signal (similar to cordless phones) would solve the interference problem, but now you'd need a special receiver for every radio in the house.
     
  4. May 1, 2008 #3

    f95toli

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    It is of course possible to build such a transmitter, but the problem is that they are illegal in most countries. There are strict rules when it comes to the maximum output power of FM transmitters which means that they are limited to distances of about one meter (perhaps slightly more), i.e. the kind of range needed to transfer music from your mp3 player to your car stereo.
    Even owning a transmitter capable of transmitting 250m over the FM band is illegal.
     
  5. May 1, 2008 #4

    Moonbear

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    What you can do, rather than broadcasting over FM, is use something like Apple's Airport Express that is on your computer network and has a jack in it to plug in external speakers (the small kind that plug into an earphone port). You can use that as a relay on your wireless network, it doesn't have to be where your internet cable comes in and can instead be located where you want to place speakers. I use that for playing music in my house. I have my computer upstairs where I play the music on the computer speakers and then relay it to the airport express downstairs that has another set of speakers plugged in so I can listen throughout the house.
     
  6. May 1, 2008 #5

    JPC

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    But why 250m is illegal ?
    if i draw a 250m circle around my pc, it doesnt go out of my parents property.
    So meaning that we are not stopping anyone from lissening to any radio frequency intervals.

    Or then :
    a kit of special frequency modulator + special frequency reciever

    Or then :
    A Amplitude modulator, no-one broadcasts on AM now, so, i dont think that would disturb anyone
     
  7. May 1, 2008 #6
    obviously it's illegal for those who are within 250m of someone else. if you really want it you'll just have to build it yourself. i bet it wouldn't be that hard to turn one of those ipod things into a higher powered one.
     
  8. May 1, 2008 #7

    Evo

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    I know a lot of people whose homes have intercoms in all of the rooms and can play music over them.
     
  9. May 1, 2008 #8

    Mech_Engineer

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    FM transmitters like you're describing do exist, however I think their range is limited to about 20-30m. Power limitations by the FCC dictate how powerful those transmitters can be, and thus limits their maximum range.
     
  10. May 1, 2008 #9

    f95toli

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    No, they ARE illegal, you need a permit to own one. The restrictions in most countries are very strict when it comes to owning radio transmitters that operate in the FM band. Whether the broadcast actually reaches someone else is irrelevant, it is the device itself that is illegal (and YOU pay the fine, not the company that made it).

    Even MP3 players with built in FM transmitters (range of couple of meters) are illegal in many countries (although some countries in Europe changed the law recently to allow low-power devices, I think there were some decision taken at the EU level).

    There are a few free frequency band (e.g. the 2.4 GHz band) that you are free to use, but most bands require a permit of some sort.

    Note that it is illegal even to attach a bigger antenna to a legal low-power transmitters.

    (I actually work at at an institute where transmitters like this are sometimes tested to make sure they are legal, although fortunately I do not belong to that division).
     
  11. May 1, 2008 #10

    JPC

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    I just want one that can broadcast like 50 meters away outside.
    Is 100 Milli wats enough ?

    Could anyone llink me from ebay an example of an apropriate one (sending through FM, and recieving on a normal FM radio) ?
    when i search on ebay, i found lots with mac, but i am not quite sure what they mean. I have a Ipod touch. Does that mean i can buy a kit of FM transmiter (for a Windows PC), with a FM reciever on my ipod ?
     
  12. May 1, 2008 #11

    mgb_phys

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    There are lots of small low power transmitters.
    The idea is that they plug into your Ipod and transmit on a spare FM frequency which you can then tune your car radio to and so listen to the iPod while driving.

    If you want to use one with your PC don't get an iPod specific one, they generally mount onto the custom connector on the bottom of the iPod - you want one with a standard 3.5mm headphone plug (assuming your PC has a headphone socket)

    Technically they may be illegal in some areas but low power ones are tolerated.
     
  13. May 1, 2008 #12

    jtbell

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    That would obviously depend on how big the receiving antenna is. You could probably get away with a very small amount of power if you were willing to carry around an antenna like this one. :biggrin:
     
  14. May 1, 2008 #13

    Moonbear

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    Why do you need to send it through FM? I already suggested another way to do it without using FM signal at all.

    Or, just get bigger speakers and turn up the volume. :biggrin:
     
  15. May 2, 2008 #14

    JPC

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    Well, i want to send via FM because AM doesnt exist anymore here

    I found on internet what i need i think :
    http://www.ccrane.com/radios/fm-transmitters/fm-transmitter.aspx

    With this i could broadcast my internet radio to the yard no problem i think
    but it doesnt precise the range

    And even if its illegal, if the range is 50 meters for example, how are they going to find me out ?
    I mean , i live in France on the countryside, i dont expect police cars with FM detectors coming around here
     
  16. May 2, 2008 #15

    BobG

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    Here's one version of USB FM transmitter.

    It says nothing about the power and range. I would assume it keeps the power within legal limits, but that doesn't guarantee it'll suit your needs.

    A search for "usb fm transmitter" brings up several other options. Here's another one. It has a range of 50 meters.
     
  17. May 2, 2008 #16

    JPC

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    The First 1 looks good,
    and the second one sends on mostly used frequency (in my zone), but i only have 2 neighbors.

    If i am sure the first one sends on a 50m range, then it will be Ok
     
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