On Tuesday the 7th of April 2020, a remarkable contact was made with the FT8 digital mode on 432 MHz between D4VHF on the Cape Verde Islands off the coast of Africa and FG8OJ in Guadeloupe in the Caribbean.
This was the first 70cms trans-Atlantic contact without using satellites or the moon. The most likely mode of propagation was marine ducting with the signal being trapped close to the ocean.
To put these remarkable contacts into some sort of perspective, remember that the distance from Newfoundland to Ireland across the North Atlantic is 3,000kms.
On a technical level, this radio contact was made possible by the recently-developed FT8 digital modulation scheme, which is designed to transmit a minimal amount of data (basically just a pair of callsigns) at only a few bits per second, so as to make even extremely weak signals detectable. The “dB” column in the screenshot illustrates that the received signal strength was roughly 100 times weaker than the background noise.
- Marine ducting
- Moon bounce