Report From The Department of Mechanical Transmitters - We all know that real transmitters must have tubes the size of wine bottles with filament currents measure in many amps. But powerhouse trans-oceanic radio stations existed before the age of tubes. What did they use? Why mechanical transmitters of course. The original Marconi transmitter at Bolinas was the standard 230kW rotary gap. It was driven by an electric motor with an 500cps alternator on the same shaft that provided voltage to the rotary. It was housed in its own alloy enclosure which was then housed in a cork lined spark chamber intended to deaden the crashing din of the spark. To no avail according the the literature of the time. You could apparently hear that thing for a mile they said. In 1920 came what I consider the be the peak of transmitter development, the Alexanderson alternator. This stupendous machine, with its multiple tuned antenna, magnetic amplifier, liquid rheostats and tuning helices put out 200kW. There were two of them at Bolinas. And were talking true CW here, not a damped wave like the spark transmitter. You could (and they did) modulate the thing. It was an Alexanderson alternator that first put voice across the Atlantic. This was all high power, low frequency (15kc to 25kc) stuff with a giant antenna to match. There is one still operating (on 17kc) in Sweden, Ernst Alexandersons home country. One of our guys has made the pilgrimage to see it run and has actually touched the sacred casting of the base of the machine. He has not washed his hand since.
Posted on: Wed, 08 Oct 2014 23:32:05 +0000
Trending Topics
Recently Viewed Topics
© 2015