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POLDHU

Notes:

Before I begin I would like to make the comparison between amateur radio and QRP in particular and commercial telecommunications.
Amateur radio is mike or key to earphone, commercial telecomms is via telephone or teleprinter with radio stations, telephone exchanges and switching centres etc in-between. Perhaps a simplification but………..
In the radio circuit the difference between a short QRP contact and a reliable all day, everyday link is antenna gain and transmitter power. And whereas amateurs are happy with a 10dB SNR, on a commercial telephony circuit one would like but did not always get 30dB SNR.
Starting at the beginning
In 1901 the initial attempts to span the Atlantic using electromagnetic waves used electrical methods of generating signals in the LF spectrum.
It was nearly ten years after Marconi’s pioneering venture in 1901 before powerful VLF arc transmitters and valve receivers established a trans Atlantic telegraphy service, reliable enough to compete with the established cable systems.
The transmitter technology was somewhat crude ranging from quenched sparks to continuous wave arcs.