From Hobby to Professional

Category: Projects/mods

  • An Easy-to-build Active Small Loop Antenna for Urban Indoor MW/SW Reception

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    by

    Alfred But
    in

    Motivation I am living in a downtown apartment where an outdoor “large” antenna is impractical. My only feasible location for a fixed antenna is at the balcony. Obviously for SWL-ing at frequency below ~15MHz, only electrically small antennas can be used. Moreover man-made noise is very high in my area, rendering a whip antenna unusable.An…

  • A low cost comb generator

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    by

    Alfred But
    in

    A comb generator is a simple but useful piece of equipment. Most comb-generators rely on a Step-recovery-diode (SRD) to create very narrow pulses which are rich in harmonics. Unfortunately SRDs are expensive, hard to find and very fragile. The above circuit and figure show one low-cost design that replace the SRD with a PIN diode.…