DECT Microwave - question

Discussion in 'General Electronics Chat' started by msd123, Feb 25, 2008.

  1. msd123

    Thread Starter New Member

    Feb 25, 2008
    I have a DECT system, which incorporates an answering machine in the base station. I no longer wish to use the DECT handset (am going back to a wired phone) but want to keep using the answering machine. Consequently, there will be no point in the base station generating microwave output, so I want to disable this. There is no way of doing this from a configuration standpoint, so I opened up the unit and there is a vertical wire connected to the motherboard that feeds into the aeriel housing.

    My question is this : if I simply snip off the wire where it connects to the motherboard, will this result in the cessation of microwave generation or will they continue to be generated (but in a diffuse way) ?
  2. SgtWookie


    Jul 17, 2007
    Your inquiry lead me to this paper:
    Medical warnings needed on DECT cordless phone use

    Very interesting, indeed!

    Apparently, leaving the handset on the base does not turn off the RF signal.

    Snipping off the antenna will certainly change the electrical characteristics of the RF output stage, it might even cause some of the transistors to get fried. I suspect that your base unit will still emit RF for a time, but it will likely be at a different level.

    What you might try is to snip the antenna, and replace it with a non-inductive resistor that measures 50 Ohms, one end connected to where the antenna was connected, the other end connected to ground. Try using a 2-Watt carbon resistor. If you only have 1-Watt resistors available, try using two 100 Ohm resistors in parallel.
    Two Watts is just a guess, as I don't know how much power your base is radiating.

    However, the 50 Ohm resistor will act as a "dummy load", dissipating the RF energy as heat rather than radiating it.
  3. msd123

    Thread Starter New Member

    Feb 25, 2008
    Thanks for the informative reply.

    As I'm not a dab-hand with a soldering iron, could you explain what would be the downside of merely earthing the existing aeriel wire without adding the resistor ?
    (my guess : I would probably end up with an impedance mismatch, with unpredictable results i.e. possible damage to the unit, but at least there would be no radiation leak ?).
    Thanks again.