Gregory's Server(the frequency was quite a bit below standard AM broadcast, typically around 15-20KHz.)
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11 comments
 there are so many cool details to this technology i had to leave out. but watch this video. you'll see amazing things like high voltage relays quenched with compressed air, water cooled load resistors, synchronous motors, and really scary 400V switches. the facility also has an informative website: https://grimeton.org/ and if you can't make it out to Sweden, there are virtual tours available: https://alexander.n.se/en/virtual-visit-to-saq-grimeton/ for further reading, here's a useful paper. https://www.navy-radio.com/xmtrs/vlf/alexanderson-mayes-1975.pdf  @tubetime OMG it runs off 2-phase because it's from a very particular time and place in the US. @tubetime OMG the air-quenched relays are scary, and they're just right out there. @tubetime Thanks for posting this; on my list for my next visit to Scandinavia. @tubetime apparently someone made a modern receiver out of relatively equivalent-level technology http://www.wireless.org.uk/mechrx.htm  @tubetime |
incredibly, there is still an *operational* Alexanderson transmitter! it is called SAQ Grimeton and they fire it up twice a year.