Hi October 21, 2014. How time flies even tho it has no wings.

Good Morning.

We were discussing the Sprtk Gap and the great innovation in the receiver section with the intro o f the galena diode(actually a Schottsky!) and vacuum tubes. A bit on vacuum tubes or valves as the British called them. Credit should really be given to Edison. He invented the light bulb and the vac tube came about with experiments on his vac lights. Names like Fleming, De Forest, etc were associated with the vac tubes.

In the beginning, there was only the light bulb. A filament inside a vacuum which lighted up and did not burn up since there was no oxygen.  A second element was placed inside and when a battery with voltages in the 45 V range was place across the lighted filament and the second element, lo and behold, current was transferring from the filament to the second element to be later called the Plate. This was the  diode! And better thna the galena crystal. so, tubes were first used as diodes to convert AC RF to DC. A mid element was then place in between the filament and the Plate. Plus was on the Plate. It was called the Grid. It was discovered that when the Grid was given a very tiny plus current, it speed up the rush of current from the filament, to be later called the Cathode, to the Plate. Eventually, the Cathode was a separate element around the filament which heated up with no physical contact to one another. This was the TRIODE! And this was the first AMP. A tiny signal can control a stronger flow of current. There was an explosion of radio tubes in the 30's and 40's. Five tube table radio receivers became a household item and soon the hi fi's were in vogue. Two way radios became realities in WW2 which also saw the use of valves to control rockets built in Germany. But the tubes were bulky, fragile and heated up. They consume lots of power. In the late 1940's, the Americans discovered transistors. By the 1950's, small pocket radios started to appear using no more than 4 cells or a 9V battery. Sony Corp was in fact at the forefront selling its pocket radio. The transistor was a 3 element device using germanium. Bell Labs started with PNP's. The emitter goes to ground, thus most of the Japanese radios were PNP radios using Germanium transistors with the suffix 2SA for RF trannies and 2SB for audio trannies. For higher current trannies, the 2SC and the 2SB trannies appeared which were now NPN'c and Silicon. Silicon is cheaper and soon, trannies were plentiful and cheap.