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AM Radio Transmitter

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Uploaded by on May 3, 2009

Better Sound with Easy Circuit (using the First Quadrant Modulator).
More information
http://www.juno.dti.ne.jp/~mkatsube/download/download.html
日本語:http://www.juno.dti.ne.jp/~mkatsube/download/download-j.html

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  • Hi,

    At the modulator/multiplier (TR101 Emitter), the carrier doesn't have negative voltage.

    Could you refer to Figure 3 or 4 in downloaded document (pdf) from my homepage?

    Carrier swings 0V and positive voltage . Negative voltage (III quadrant region) generates with LC resonator.

    So modulator works at 1-quadrant region.

    From this, I call 1-quadrant modulator.

    Thank you for the comment.

  • Actually, you have a 2-quadrant modulator/multiplier. The carrier swings both positive and negative (I and III quadrants) while the modulating signal (sine plus constant) is confined to the I quadrant.

  • 300uH is not so critical.Q of the resonator is critical thing. R107 (dumping resistor) in Figure 1 controls Q. And R107 also working for prevention self oscillation. If you have strange phenomenon, please adjust R107.

    I think 680uH/470uH (tap) is not bad choice.

    About an external antenna, remaining one jack is for external antenna. 3rd picture in the video, plunger is my favorite external antenna!

    Thanks.

  • One question about the ferrite loop-stick antenna.

    The specification is for 300uH. I found a 470uH with no tap. I found a second ferrite Loopstick antenna 680uh with tap at 470uh. How critical is the 300uH?

    What adjustments do I need to make to use this?

    Also can I use and external wire antenna? I note you have two phone jacks on the side, one for audio in. What is the second phono plug for? Thanks.

  • Hi,

    Basically you can use the same circuit in the U.S. too. I mean you don't need modification. The reason of this is Japan has similar to your band plan (535k to 1605k with 9k spacing). My transmitter works at 1030kHz.

    Thank you.

  • How DO you modify the circuit to play on USA.... MW band (BCB or broadcast band).

    USA as you know is 530Khz to 1700Khz with 10Khz spacing..... Thank you.

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