"I am often asked how radio works. Well, you see, wire telegraphy is like a very long cat. You yank his tail in New York and he meows in Los Angeles. Do you understand this? Now, radio is exactly the same, except that there is no cat." : Albert Einstein
One of the things that always fascinated me about radio was the ability to take discrete components and craft something that could pluck invisible radio signals out of the air. Once I learned more about electronics, some of the magic was replaced by admiration for the many generations of engineers and experimenters that had developed the radio art. Until recently, the theory behind crystals had not solidified (crystallized?) in my mind and so they remained one of those "mysterious devices".
The following film, like most produced during WWII, is a thorough explanation of the history and technology behind radio crystals. It was produced at a period when crystals were instrumental in securing reliable communications between military units, saving lives and coordinating the moment of supplies, troops and equipment.
Most of us have seen glass and plastic being recycled however recycling of consumer goods made with multiple materials can be much more challenging. In the past Christmas tree lights have been burnt to obtain the copper but this releases a slew of toxic chemicals into the air from the burning plastic. A better solution has been found by a Chinese recycling company that specializes in recycling all the material from light strings once they have served out their time on trees, roofs and gardens.
Living in America we are usually located a long way away from the source of the goods we use and consume each day. Sometimes we are reminded of where our food comes from but what about the other goods?
The Blacksmith Institute has produced these two videos showing how gold is refined using mercury and the impact that has on the miners. They've also started to supply the miners with some simple tools to make the process safer and more efficient.
Something to think about when making your next electronics purchase as almost every electronic device contains at least some gold.
