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Since extremely-low-frequency radio waves are used by submarines for some simple, low-transmission-rate communications, why can't those same wavelengths be used for submarine radar? It may not be ideal, or highly precise, but couldn't it still provide some useful information?

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    $\begingroup$ According to the Wiki page, en.wikipedia.org/wiki/Communication_with_submarines , ELF is not used by submarines because they can't take a feasible antenna with them. Also you couldn't use ELF to pinpoint an object on the scale of tens of meters because the ELF wavelength is a million meters. $\endgroup$ May 20 '19 at 21:54
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There are likely many reasons why ELF radar is impractical. Here are two. The wavelength at ELF frequencies exceeds 10,000 km. A radar using that large a wavelength will not be able to locate anything very precisely. In addition, radiating and receiving radio signals efficiently requires an antenna size of a significant fraction of a wavelength; probably too big to fit on a submrarine.

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if you use a zig zag length of wire like the steel fluid line in a radiator you could easily get an antenna long enough. thats not the problem. the power required to run elf radios might mean the subs have to be slowed or stopped to divert enough power and thats if the alternators/generators can handle it. if that unlikely scenario is accomplished one would have to solve the problem of the rf radiation burning people.

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  • $\begingroup$ Why can they be used for communication and not with a radar? Would a radar require significantly more power? Why usual radars that use higher frequencies don't burn people, as you said an elf radar would? $\endgroup$
    – Prallax
    Aug 16 at 6:14

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