LEARNING CURVE
CQ is in the middle of celebrating its 75th year of serving the Amateur Radio Service. Within those 75 years, technology and ham radio experienced tremendous change. Arguably, one of the biggest changes involved the transition from vacuum tube technology, which was state-of-the-art in 1945, to transistor, or solid-state, technology. Even though today’s state of the art has progressed to integrated circuits and microcontrollers, tubes and transistors are still major components of ham radio technology. Let’s take a closer look.
Hollow State
Vacuum tube technology, also fondly referred to as “hollow-state” because of the vacuum inside a tube’s glass enclosure, revolutionized the field of communications. Before the advent of tubes (valves if you’re century, distances were limited to a few miles. “Brute force” was the rule de jour. More power output equated to a few more miles. However, positive changes were on the horizon. The first vacuum tube, invented in 1904, is credited to John Ambrose Fleming (), a British electrical engineer. Fleming’s diode vacuum tube consists of two electrodes: The cathode is negative, and the anode, or plate, is positive (). The diode tube will let electric current flow in only one direction (negative to positive), so it is used as a rectifier. In 1906, a brilliant inventor from Council Bluffs, Iowa, Lee De Forest (), invented the triode vacuum tube. De Forest discovered that by inserting a third electrode called a control grid between the cathode (negative electrode) and the anode (positive electrode) of the existing diode tube (), he could amplify a signal! This new tube, he called the Audion ( and ), revolutionized electronics and communications. The triode’s ability to amplify signals made it possible to increase power outputs, but even more importantly, allowed receivers to detect and amplify weak signals. Communication range for radio amateurs increased tremendously.
