矿石收音机
维基百科，自由的百科全书
矿石收音机 第一次由Greenleaf Whittier Pickard在大约 1900年 制造，并且使用条形晶体矿石来探测 无线电信号。
目录 |
[编辑] 历史
[编辑] 早期
人们第一次制造和使用了简单低价的矿石收音机不需要电池或电能。即使在第一次世界大战之后电子管收音机被普遍使用, 矿石收音机依旧非常流行, 特别是在业余初级无线电爱好者,和学生当中。 他们制作矿石收音机以学习基本的电子和通信知识。 早期的无线电通讯使用频率为400–1000赫兹，由交流发生器提供动力 spark gap plasma arc transmitters When these telegraph keyed Morse code signals were received, the tone or pitch of the generator was clearly heard varying the strength of the radio wave. Varying the strength in this way is called amplitude modulation. As wireless telegraphy became more widely used, the newer radio transmitters employed amplifiers that produced higher power and a tuned signal that required less bandwidth, thus reducing interference. HELLO this is all junk!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
The first radio telephone transmitters also used amplitude modulation to carry speech and music on a radio wave. The crystal set received these signals almost as well as wireless telegraph signals. AM radio stations today still use amplitude modulation at power levels up to 50 kilowatts on the U.S. broadcast band, and 1 megawatt on shortwave bands. Crystal sets with long wire antennas can still be used today, but their poor selectivity causes signal overlap on crowded broadcast bands.
[编辑] 1920－1930年代
When radio broadcasting became popular in the 1920s, many amateur experimenters bought or constructed crystal sets, often with the tuner inductor coil wound on a tubular oatmeal box or a drinking glass. This led to a series of adventure novels, the Radio Boys books, similar to the Hardy Boys books.
When electronic amplifiers and oscillators were invented, they were almost immediately put into service, rendering crystal sets obsolete first by the much more sensitive vacuum tube regenerative circuit designs and then the highly selective superheterodyne receivers.
During the Great Depression a crystal radio detector could be constructed from an inexpensive or homemade galena crystal and a safety pin. After this detector was connected to steel bedsprings (which doubled as an antenna) and grounded to household cold-water pipes, only inexpensive headphones were needed to listen to the world.
[编辑] 1940年代
GIs during World War II constructed similar radios from rusty razor blades and pencil lead, the iron oxide crystals of the rust replacing the galena crystal and the graphite of the pencil lead substituting for the safety-pin wire. These crude, but functional, radios were nicknamed foxhole radios.
[编辑] 晚期
Crystal sets were the most common form of radio listening device for non-professionals in the early 1920s. A century after their first use, hobbyists still build and tinker with— and listen to— crystal radios constructed from just a few parts.
The most common modern design uses a coil for a tuner, and a semiconductor diode instead of a crystal. The output is usually from an earphone speaker. A lengthy antenna wire (15m (40ft) or more) is still helpful to get good sound. A modern design for a "trash radio" is constructed from a tin can and some wire.
In the amateur radio world, particularly amongst QRP operators, crystal recievers are sometimes used in homebrew projects. The most notable is the Pixie2 CW transceiver, an inexpensive kit radio which combines a small crystal-powered transmitter with a crystal reciever attached to a small audio amplifier.
[编辑] 构成
Receiver
矿石收音机是一个简单的无线电 接收机, 由长导线天线, 用于选择信号频率的调谐器和由二极管解调器构成的检波器组成, 这个检波器一般是用锋利的线或者针押在房子f a sharp wire or pin pressing against a sensitive point on a galena mineral crystal in a holder.
A semiconductive mineral crystal, usually lead sulfide (galena) or cadmium sulfide is fixed inside a brass cup and the radio operator finds the loudest signal by touching the wire, called a "cat's whisker", to various points on the surface of the crystal; some commercial kits substitute a discrete silicon or germanium diode for the cat's whisker assembly, and it is claimed during World War II that GIs built sets with rusty razor blades (modern razor blades, being generally made from stainless steel, do not rust sufficiently to do the same). The radio is entirely powered from the radio waves it receives. The most expensive part can be the length of antenna wire.
The detector extracts the 调幅 from the radio signal by 整流器 it, and provides an audio output in proportion to the strength of the signal coming from the antenna. The entire set is passive, requiring no external 电功率. 因为没有放大单元，因此需要灵敏度较高的耳机，因此也不可能控制音量。
[编辑] 谍报
据说矿石收音机可能依然被间谍使用。矿石收音机没有振盪器，因此反间谍组织不能侦测到被监听的频率。
[编辑] 参看
[编辑] 外部链接
- 玩具矿石收音机Volumes One and Two 商用的矿石收音机图片集， 1920－最近，包括rocket, 微型, 口袋型,和众多的新型号
- G. W. Pickard 美國專利 836531
- G. W. Pickard 美國專利 876996
- 使用和改造矿石收音机 无线电爱好者项目(2000年8月13日)
- 矿石收音机社区, 关注制造和试验无线电技术
- Field, Simon Quellen, 制作简单的矿石收音机 科技玩具
- Stay Tuned. 矿石收音机计划和项目
- 无线电原件历史.
