Welcome to DU! The truly grassroots left-of-center political community where regular people, not algorithms, drive the discussions and set the standards. Join the community: Create a free account Support DU (and get rid of ads!): Become a Star Member Latest Breaking News Editorials & Other Articles General Discussion The DU Lounge All Forums Issue Forums Culture Forums Alliance Forums Region Forums Support Forums Help & Search

General Discussion

usonian

(27,536 posts)

3. VERRRRRRRRRRRY low frequencies to penetrate through a lot of water.

Reply to underpants (Reply #2)

Fri Jul 10, 2026, 12:13 AM

Friday

demand a very long wavelength, hence antenna.

That's actually short for the wavelengths and frequencies involved.

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

Electromagnetic waves in the ELF and super low frequency (SLF) frequency ranges (3–300 Hz) can penetrate seawater to depths of hundreds of metres, allowing signals to be sent to submarines at their operating depths. Building an ELF transmitter is a formidable challenge, as they have to work at incredibly long wavelengths:

stuff about ground-based transmitter projects from the past ...

The usual half-wavelength dipole antenna cannot be feasibly constructed, as that would require a 1,800 km (1,100 mi) long antenna.

Edit history

Please sign in to view edit histories.

Recommendations

2 members have recommended this reply (displayed in chronological order):

underpants ultralite001

3 replies

= new reply since forum marked as read

Highlight:

Put me in, Coach... [View all] ultralite001 Thursday OP

I suspect it's because of the (alleged) new threats on his life by Iran. usonian Thursday #1

I'd passed over that graphic before. The trailing antenna is 5 miles long? underpants Thursday #2

VERRRRRRRRRRRY low frequencies to penetrate through a lot of water. usonian Friday #3