[anfractuosity]

It looks like, as the crow flies distance between Chicago and Frankfurt, would take a pulse around 23ms to arrive, at the speed of light. It looks like for a LEO satellite, the round trip time, is around 40ms.

They mention it uses the ionosphere, so curious exactly how long it takes the short-wave pulse to arrive.

[cynwoody]

HF radio reflects off the ionosphere's F-layer, located about 100-200 miles up. To get from Chicago to Frankfurt requires several hops between the ionosphere and the earth's surface. The hop length is one or two thousand miles.

Satellites such as Starlink operate in low earth orbit at about 350 miles, significantly above the F-layer. Also, they introduce repeater delay when they relay a data packet. To get from Chicago to Frankfurt would require relaying the packet thru multiple satellites. So, greater distance (even if passed by laser between satellites) plus repeater delays.

Also note that satellites in LEO are the only option. Geosynchronous satellites are completely out of the game due to the much greater distances involved.

Radio ham blog post discussing HF propagation:

    https://www.pa9x.com/long-path-or-short-path-propagation/