4 ms·
Why no radio ping?
by ape4 13y ago
Why no radio ping?
- ISL 13y agoDeep ocean water is opaque to all but the lowest frequency RF. http://en.wikipedia.org/wiki/Extremely_low_frequency http://en.wikipedia.org/wiki/Extremely_low_frequency
- deleted 13y ago[deleted]
- cynwoody 13y agoWhich is why, during the Cold War, the US maintained very powerful long wave transmitters, both land-based and airborne. Using VLF†, they could send the nuclear launch codes to the nuclear missile submarines without the subs having to break the surface and create a possible radar return. They kept an airplane aloft 24 hours a day carrying a SAC general. In the event of war, it could reel out a long-wire antenna a couple of miles long from its tail and send out the codes. †http://en.wikipedia.org/wiki/Communication_with_submarines#Very_low_frequency http://en.wikipedia.org/wiki/Communication_with_submarines#V...
- eitland 13y agoI wonder how this can have worked; according to my understanding VLF transmission for underwater reception needs very much power. Did they bring really a powerful generator in the plane?
- brc 13y agohttp://en.wikipedia.org/wiki/Naval_Communication_Station_Harold_E._Holt http://en.wikipedia.org/wiki/Naval_Communication_Station_Har... This says 1 MW power. I would say a mobile platform could get away with much lower power.
- cynwoody 13y agoAccording to the Wikipedia†, the aircraft in question had a 200 kw transmitter, but the article is a bit vague about VLF in particular. The idea, of course, was that while, hopefully, the ground stations would get the message out, there was that airplane you couldn't count on knocking out in a first strike. †http://en.wikipedia.org/wiki/TACAMO http://en.wikipedia.org/wiki/TACAMO
- wglb 13y agoSince seawater is conductive, radio waves die out quickly. Thus, these use audio, which travels nicely in seawater.