Use As A Power Source
A crystal radio tuned to a strong local transmitter can be used just as a power source for a second amplified receiver for distant stations that cannot be heard with a plain crystal radio.
There is a long history of unsuccessful attempts and unverified claims to recover the power in the carrier of the received signal itself. Traditional crystal sets use half-wave rectifiers. As AM signals have a modulation factor of only 30% by voltage at peaks, no more than 9% of received signal power is actual audio information, and 91% is just rectified DC voltage. Given that the audio signal is unlikely to be at peak all the time, the ratio of energy is, in practice, even greater. Considerable effort was made to convert this DC voltage into sound energy. Some earlier attempts include a one-transistor amplifier in 1966. Sometimes efforts to recover this power are confused with other efforts to produce a more efficient detection. This history continues now with designs as elaborate as "inverted two-wave switching power unit".
Read more about this topic: Crystal Radio
Famous quotes containing the words power and/or source:
“I swear by the mighty power of Amon-Ra, whose anger can shatter the world, and by the dread power of Set, that I will never betray my trust as High Priest of Karnak.”
—Griffin Jay, Maxwell Shane (1905–1983)
“Because relationships are a primary source of self-esteem for girls and women, daughters need to know they will not lose our love if they speak up for what they want to tell us how they feel about things. . . . Teaching girls to make specific requests, rather than being indirect and agreeable, will help them avoid the pitfalls of having to be manipulative and calculating to get what they want.”
—Jeanne Elium (20th century)