The Diode Handbook

Microsemi was a company founded in 1960 by Don Dickenson as Dickenson Electronics. It was started in Scottsdale, AZ; and is still in Arizona today though it's present headquarters is in Aliso Viejo, California. The company was acquired by Siemens in 1974 and then Microsemi in 1982. They are still one of the worlds major manufacturers of diodes. That includes those used to rectify RF signals. Some of their components are on board the Mars Rover.They are so bin in fact that they attempted to acquire a competitor in 2008 and were stopped by the DOJ as it would create a monopoly on certain components.

What I like about this booklet is that it's not just superfluous marketing propaganda. It includes a short history of the company but also an extended explanation of what diodes are and how they're manufactured. It even has a tiny glossary covering tech jargon that even I was unfamiliar with.

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Regenerative Microwave Converter

This December, Nihon Dengyo Kosaku Co. debuted a microwave regenerative converter for 2.45GHz-band rectennas. consumers don't think about it, but microwave ovens are fundamentally similar to microwave antennas. The primary difference is that a microwave oven is designed to contain the "broadcast" so it can be converted to heat energy when it encounters mass i.e. your lunch. This process is called dialectic heating. Don't be surprised this gadget was invented in China, the microwave itself was invented in Japan in 1955. It wasn't introduced to Americans until Amana imported it in 1967.

So here's how this widget comes in. Your microwave isn't 100% efficient. Actually if you've ever looked at it's power consumption you already kow it's a bit of a hog when it's running. That's because much of the microwaves just bounce around and dissapate, they are not all absorbed by their intended target. That  means a portion of those aren't converted to heat and are totally wasted. An average consumer microwave oven consumes 1100 watts of electricity to produce 700 watts of power. That's an efficiency of 64%, though it'd obviously vary. To be fair a lot of that is just heat loss.

This rectenna receives the microwaves in your microwave oven and converts that surplus energy to electricity. The reason this regenerative converter works only at a frequency of 2.45 GHz, is that it's also the frequency that all consumer microwaves operate on. Commercial microwave ovens operating 915 MHz.  I have read that some countries also use 433.92 MHz. This would be most efficient if it were used to reduce the power draw of the microwave itself, but it's as yet unknown if it will even go into commercial production. More here.

Perikon detector

Strange as it may seem, the crystal in crystal radios wore out. The rectifier was a contact metal–semiconductor point-contact junction, aka a Schottky diode. I mentioned this once before so I wont get too much into the diode. But suffice it to say that not every part of the crystal would rectify the circuit. Rectification in this case means "act like a diode." More here.
Because the whisker was made of wire or a needle, and the crystal was softer, the surface was worn by use. OK hypothetically not every "crystal" was softer, but they were almost inherently of different harnesses. The very soft Graphite was used as a whisker sometimes. and at the other end, carborundum was considered durable. So either the whisker or the crystal was experiencing wear and usually it was the crystal. So hobbyist chose a crystal and whisker based both on it's sensitivity as a detector but also it's longevity. The hunt was on from the start for a "permanent detector."

Lets look at the hardness of some known whiskers and crystals:
WHISKERS
Graphite: 1-2 Mohs
Bornite: 3 Mohs
Iron: 4 Mohs
Steel: 7-8 Mohs
Bronze: 3 Mohs

CRYSTALS
Galena: 2.5 Mohs
Zincyte: 4 - 4.5 Mohs
Molybdenite: 1 - 1.5 Mohs
Iron Pyrite: 6-7 Mohs
Carborundum: 9 Mohs
Silicium: 7-8 Mohs
Chalcopyrite: 2.5 Mohs

As narrow as that variation is, remember that the Mohs scale is only a 10 point same topping out with diamond. not every whisker and crystal worked well together and even when they did, their mismatched harnesses could be problematic. Some combinations were proprietary and many of those were discovered by Mr. Greenleaf Whittier Pickard. He found both the Zincite /Bornite rectifier and the Zincite / rectifier. He called it the Perikon Detector.

He also tested versions with iron pyrite and silicon crystals. Silicon was novel enough he patented it's use in 1906. His Zinc Oxide detector was patented in 1909. He developed one with Molybdenite the same year. More here.

Karl Braun rectifies

Yesterday I covered an improvement in crystal rectification. While it may seem crude, it was an advancement. And like any "break-through" it begat others, and was based in those that preceded it. I specifically noted Karl Braun. He is best known for invented the first cathode-ray oscilloscope in 1897. It's a big flashy invention with a fluorescent screen. But he also defined the basic principles of rectification, which while not as ostentatious was more important.

Rectification simply put is converting AC to DC. In radio this is a crystal detector, or a diode. Braun had been studying the conductivity of metal salts in solution, what we call electrolytes. he found that they conducted electricity even when not dissolved. He then made an examination of metallic sulfides. He discovered that in many metal sulfides the electrical resistance varies with the magnitude and polarity of the applied voltage. Viola! rectification. More specifically this was the "point-contact rectifier effect."

He went on to write a paper in 1874 on current flow through metallic sulfides. This was before radio, so it's implications were not immediately obvious to him. It was Sir Jagadis Chandra Bose, who made that leap and applied to patent the idea in 1901. In the U.S. we teach that Marconi invented radio. In Germany I understand, they're a little better at mentioning that Dr. Braun shared that 1909 Nobel Prize for physics with Guglielmo Marconi for developing the "Wireless."

Unlike Losev, Braun was an academic. He'd even published scholarly articles while in high school. He attended the University of Marburg and earned his Phd at the University of Berlin in 1872. He taught physics at the University of Strasbourg. His career is well documented. But I find two different stories of his death. One tale tells of him defending his patents on his discoveries. In 1915 he traveled to New York City to go to court. the intimation is that he is defending a closed circuit design that improved upon Marconi's open circuit design. The other tale has him headed to New York to defend the German Telefunken wireless station at Sayville, N.Y. Defending it from none other than Marconi. I lean toward this second version as I can confirm that in 1915 said trial was at least extant.

Both stories end with him being detained because of his German citizenship. Unable to return home, he bought a house in Brooklyn, and died in April of 1918 without having ever returned to his homeland.