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Today - September 27, 2023

Area 50

Area 50 is a collection of unusual, difficult, or simply lightly documented projects. Much of the information in Area 50 is intended for experienced hobbyists - not beginners. The information may be incomplete or even incorrect and readers are assumed to have sufficient knowledge of the areas covered to evaluate the suitability and veracity of the information. Many projects will have kernels of information that are useful for other purposes and those will be mentioned at the end of the page.

The Amazing All-Band Receiver

The Amazing All-Band Receiver is basically a diode detector followed by a high-gain audio amplifier. This is not a multi-band receiver; it picks up everything at once! The detector uses a biased Schottky diode for excellent sensitivity and bandwidth; the detector will detect signals from below the AM broadcast band up to the microwave bands. The number of interesting signals is surprising; it is fun to drive around listening to the numerous strange sounds.

By trying different antennas and locations, this receiver has picked up AM radio stations, FM stations, TV video (buzz), car lock transmitters, cell phones, and even the microwave oven (a whoosh-whoosh sound as the microwave spreader rotated). It isn't clear how FM stations are demodulated; perhaps the antenna Q is sufficient for slope detection. (See reader Karen's excellent theory.) Even the familiar buzz from a narrow-band FM pager transmitter has been heard - somehow. There are some mysterious signals out there, too! What is that occasional descending whistle over by the highway? Some vehicles emit a curious buzz, too. If you hear a mysterious click-click now and then, its your cell phone! Don't expect to tune in international shortwave stations. This receiver is for strong, local sources. The advanced experimenter will find it useful as a detector section for low power tuned receivers.