Reg Edwards wrote:

A transatlantic coaxial cable, 2000 miles long, has an overall
attenuation at 5 MHz of around 4000 decibels. . .

Just to get a little context here. . .

Years ago when I was a little bored, I determined that the ratio of the
light output from a common two cell flashlight to the entire light
output of the Sun is a mere 280 dB (10^28). So if you attenuate the Sun
by 280 dB you get the light of a flashlight beam. Well now, if you took
that flashlight beam and attenuated it again by the same amount, then
did that again, and again, 14 times altogether, you still wouldn't quite
have totaled 4000 dB. It's a staggering number, incomprehensible except
by some pretty abstract thinking. It's real, though. I remember reading
a paper long ago about transatlantic cables, and those are the numbers
they work with.

Roy Lewallen, W7EL