[LMB] OT: Tech marches on

[Matija Grabnar]

On 14/12/2021 10:22, Raymond Collins wrote:
> ELF or extremely low frequency allows submarines to receive secure
> communications from the US  deep underwater.
Yes, but only for sending to submarines, submarines have to surface to 
reply.
>   I'm uncertain how deep
> underwater the signals can be received but I know the the ELF antenna
> cables went underwater.

I don't think that's true. The radio very long radio waves penetrate 
water, but the antennas are still in the air, not underwater.

https://en.wikipedia.org/wiki/Jim_Creek_Naval_Radio_Station

https://en.wikipedia.org/wiki/VLF_Transmitter_Cutler

>   The communication rate was very slow.
With a base frequency of 24kHz (and probably a suitably narrow band), I 
am not surprised. The wiki page I linked mentions that only coded 
messages can be transmitted, not speech.