Loudspeaking Crystal Radio

Discussion in 'Wireless & RF Design' started by vu2nan, Sep 24, 2015.

  1. vu2nan

    Thread Starter Member

    Sep 11, 2014
    43
    10
    This is the speaker variant of my series-tuned crystal radio with an improved detector.

    [​IMG]
    Loudspeaking Series-tuned Crystal Radio Schematic

    Replacing balanced armature headphones (impedance around a few hundred ohms) with a low impedance speaker required the use of an output transformer.

    A power transformer, with its inherent thick conductors, appeared to be an ideal substitute for a low-loss output transformer.

    Trials with transformers rated 230V/24V-2A, 230V/24V-5A and 230V/24V-15A proved the last one to be the best.

    [​IMG]
    Loudspeaking Crystal Radio

    Reception of the lone local 200kW 612kHz AM broadcast station, located 20km away, was quite good.

    Antenna was a 60' long wire.

    Performance was equally good in the parallel-tuned configuration.
    [​IMG]
    Loudspeaking Parallel-tuned Crystal Radio Schematic

    Regards,

    Nandu.
     
    Last edited: Apr 30, 2016
    ISB123 likes this.
  2. ISB123

    Well-Known Member

    May 21, 2014
    1,239
    527
    Nice,you even used the original breadboard! :)
     
  3. Willen

    Member

    Nov 13, 2015
    138
    12
    If there's very small power in the radio then maybe less numbers (like 100s or 200s) of turns at input of transformer kills the signal across the transformer (maybe). Can you assume minimum turns with core type?
     
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