Salvaging Parts

Discussion in 'General Electronics Chat' started by GFTMC, Jul 7, 2008.

  1. GFTMC

    Thread Starter Member

    Jan 20, 2008
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    0
    Ok. So I have an old wireless telephone, and I want to salvage as many parts of it as I can before throwing it away. I took every plug speaker and microphone I could find, as well as the antenna.

    Now I got to the hard part - I want to salvage one of the phone's transmitters. I have found a number of pieces which looks like transmitters and recieveres to me (I'll post a pic later): They are small PCBs with coils on top, connected with resistors. Only two wires per piece.

    Now I wonder - Can I use those to transmit short-range radio waves? I though about something simple, such as connecting the two wires to a source of sound, and attempting to find it using a radio scanner.

    I have absuloutly no idea wether this will work or not. Provided it won't, can you suggest a simple transmitting circuit to be used instead or in conjuction with?

    Thanks ahead.
     
  2. Wendy

    Moderator

    Mar 24, 2008
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    Depends, old phones cover a lot of ground, but I'll start by assuming you're not talking a cell phone. The early phones were pretty bad, they chattered continuously when I had my early computers on, would answer neighbors rings (and visa versa) and were barely good enough to use. They have had slow incremental advances until they are the really nice consumer gadgets they are today.

    So, what year do you think this thing was made? More than 10 years ago, 20?

    Generally it is easier to build something from scratch than to try using something like this, but if you have an application in mind...
     
  3. GFTMC

    Thread Starter Member

    Jan 20, 2008
    18
    0
    Well, the phone is quite new, although I can't tell exactly - it is somwhen between 5 and 15 years old. The piece I got has two inductors - one with an iron core. The inductors are connected serialy, without the resistors connecting them, like in the attached file (I can remove the iron core if not needed)

    I only wish to use this as some sort of a transmitter that preferebly can be discovered by a receiever I already have (An old radio which can recieve both medium waves and short waves)
     
  4. Wendy

    Moderator

    Mar 24, 2008
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    Newer phones sometimes encrypt their signals, to address the nosy neighbor issue. The phone case should have the freq written down somewhere, and FM is the norm. All of this is chancy, there were no standards (and I don't think there still are) concerning exact conventions.
     
  5. GFTMC

    Thread Starter Member

    Jan 20, 2008
    18
    0
    I see. What about using that part as a part of a bigger transmitter? Will passing electric signal through it (Like audio) be enough to make it transmit? Or should I use a pre-amp?
     
  6. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    What you're describing is likely a ferrite-core antenna. It is highly likely that it is tuned for 900MHz or 2.4GHz.

    Unless you have a receiver for those bands, it may not be very useful to you at this point in time.

    Before you spend much time on transmitters, contemplate receivers instead. If you're in the USA, you will quickly find out that the FCC has absolutely NO sense of humor if you are out of line with transmitters, and the fines are huge. If you are in Europe, they have even less of a sense of humor, and there are virtually no amateur bands open.

    The rage nowadays in the States is extremely low-powered transmitters coupled with very high efficiency receiving antennas. You can get far better results with a really good antenna than you can get with a big transmitter.
     
  7. GFTMC

    Thread Starter Member

    Jan 20, 2008
    18
    0
    Thanks for the warning and the advice. Though I only wish to transmit to very short distances - 10 meters or so.
     
  8. Primary

    New Member

    Jul 8, 2008
    5
    0
    If your goal is to have a transmitter I would just go to RadioShack or similar electronics store with a 10 dollar bill and buy a kit and make it. Then you know its specifications ( like its frequency range and power output ) and you will have something that works and you may even get a circuit explanation for it and all the other good info that generally comes with the electronics kit. The final decision on purchasing a kit or trying to make something out of an old phone would depend upon what exactly do you want to do with it. Many years ago (around 1970 or so) I had one of those 50-in-1 electronic project kits with the little booklet and all that explained how to make circuits by connecting the wires to those springs and one of the circuits was a transmitter. Many ways to make a transmitter. If you have acess to a spectrum analyzer you can find your phone's frequency with that.
     
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