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rf transceiver

Discussion in 'General Electronics' started by erdem, Feb 1, 2004.

  1. erdem

    erdem Guest

    Hi all,

    I am trying to build some transceivers on my own (-to build some door
    lockers, rf switches), but to understand the basics I started to do
    some reverse engineering on a powerhouse x-10 transceiver module.
    These things seemed to be very basic to me. I tried to measure the
    oscillator frequency by using a scope, and found out there is a 38kHz
    oscillation in the circuit(it is not like a sinus wave, but sthg like
    a binary signal 0 for half of the cycle, then it fastly oscillates
    from -1 to 1 for half the cycle-scope does not trigger this part, it
    seems like some relaxation oscillations in this part of the cycle).
    Anyways the interesting thing is; there is a small copper wire-0.5cm
    long, shaped as a half circle after the inductance in the circuit. I
    thought this might be sthg like an antenna in this device, but my
    antenna class reminded me that antenna lengths are usually on the
    orders of the wavelength. But this antenna is very short (0.5cm is
    60Ghz), is there sthg wrong with my knowledge, how does this small
    antenna work? If this is an antenna how can I get an idea about the
    radiation pattern, easily.

    Thanks,
    Adam
     
  2. Anand Dhuru

    Anand Dhuru Guest

    Hi,

    Hi,

    When you say a transceiver, are you referring to an RF transceiver?

    The X10 Powerhouse kind of devices are not transceivers in that sense;
    they take (receive) RF signals, and transmit X10 signals thru' the
    mains line, not RF.

    So, the small RF circuit you saw is just an RF receiver. The small
    copper loop is like a coil in the circuit; the main antenna is the
    external one that is coupled to the PCB thru' the plastic casing.

    The circuit for this module is available at
    http://www.geocities.com/ido_bartana/

    In my experience, it is fairly easy to build an RF transmitter, but
    the receiver is more complex; its better to buy the receivers,
    although there again there are circuits available on the internet.

    Regards,

    Anand Dhuru
     
  3. erdem

    erdem Guest

    Thanks for the link. What I have is a powerhouse x-10 transceiver
    module and a remote control chain kc674. The circuit that I was
    describing is in the remote control key chain, so that circuit should
    be an rf transmitter. If that copper circle is not an antenna, what
    does a coil do in an rf transmitter?

    Here is the link for the device I have;

    http://store.yahoo.com/asihome/rcx10remkeyc.html

    Adam
     
  4. Anand Dhuru

    Anand Dhuru Guest

    Hi,

    I thought you were referring to the TM751 / RR501 X10 transceiver;
    anyway, the actual transmitter in the keychain remote is a design that
    is pretty much standard to X10 products, and is found with small
    variations in the 5/6 - in - one remotes, the palm pads, the CM17
    Firecracker etc.

    The loop, alongwith the copper trace on the PCB acts like an antenna.
    There are also articles that describe the X10 RF protocol URL'led from
    Ido's site.

    Regards,

    Anand Dhuru
     
  5. erdem

    erdem Guest

    I thought it was an antenna too, but am I wrong about the size issue
    with antennas, shouldn't they be proportional to wavelength, etc, etc.
    This antenna is only 0.5cm...
     
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