• The Best One Transistor MW Radio Ever

    agp.cooper • 03/22/2018 at 02:08 • 8 comments

    The Best One Transistor MW Radio Ever

    Its a bold statement! Can you do better!

    It's the 636 One Transistor Reflex:

    And a video from the Internet:

    Another example:

    Here is my simulation of the 636:

    A number of changes were made:

    • Modified for 9v and crystal ear-piece output.
    • Added a 1k base resistor to stop "Colpitts oscillation".

    The schematic consists of:

    • On the far left, a the signal generator (before the the signal probe).
    • Then the short wire antenna model.
    • Then the tuning coil and tap at 10%.
    • Then the 636 circuit.

    Analysis:

    • The left analysis is of a 1 mv 1 Mhz signal modulated by a 1 Khz audio signal.
    • The audio shows a square law distorted audio output of 6 mv (a gain of x3).
    • The right analysis is of a 10 mv 1 Mhz signal modulated by a 1 Khz audio signal.
    • The audio shows a square law distorted audio output of 900 mv (a gain of 45).

    Replacing the 1 mH inductor with a 1k resistor, reduced the gain by a factor of 3:

    Increasing the tuning coil tap to 20% (from 10%) kills the tuning coil Q.

    Over to you!