Remote On

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This feature is for the user that wants to remotely turn on/off the Flex-5000 radio. This feature is a function of DDUtil and requires additional hardware to perform the actual mechanical events. The following sections describe this hardware and the user operations involved.

Theory of Operation

In order to provide a remote turn on/off function DDUtil momentarily turns on the RTS control line in a serial port. This sends a +12vdc pulse to a transistor that in turn pulls in a small relay. This relay closure connects the two wires coming from the Flex radio together causing a reset of the Power-on circuity in the radio. This reset will either turn on or turn off the radio depending on its current condition.

  • If the radio was turned on DDUtil will start PowerSDR.
  • If the radio was turned off DDUtil will close PowerSDR.


To use the Flex Remote Power On/Off feature the following prerequisite requirements must be in place:

  • Hardware
    • The radio (Flex-5000) must be modified[1] to accept remote switching.
    • A hardware circuit similar to the one shown in this drawing must be fabricated and attached to the PC serial port and the radio.
    • A free hardware serial port on the PC (can be a USB adapter).


  • Perform the radio modification.
  • Install the external hardware circuit.
  • On the DDUtil Setup form, Files tab in the PowerSDR Remote Start group.
    • In the first window select the PowerSDR file path and name.
Note! The location of the PSDR file has to be updated each time PSDR is revised.
  • In the Port window select the desired Com port where the switching hardware is attached.


  • Make sure the power supply for the radio is on.
  • Select the Start Radio selection from the Tools menu. Also, the short-cut key combination [ctrl+shift+S] can be used.
  • Shortly, the blue or red pilot light on the radio should come on.
  • Additionally, PowerSDR should start if the StartPSDR menu item is checked in the Tools menu.
  • Pressing the Power button again will power off the radio and close PowerSDR.


  1. Contact FlexRadio Systems for information about obtaining the needed radio modification. Even though this modification can be done in the field it requires knowledge of the radio and skill to accomplish and not to forget the probable loss of warranty by doing it yourself.