Speaking as a spacecraft engineer, the thing that gets me about Loeb's interpretations is that his alien engineers are insultingly incompetent.
RCS thruster plumes visible from the other side of the solar system, making no difference in the trajectory?!
And 'Oumuamua was a *terrible* solar sail.

They really missed the opportunity to open this "In otter news..."

The main thing Arthur C. Clarke missed is that an HS-601 or A2100 comsat does not have “living quarters, laboratories, and everything needed for the comfort of its crew.” There are no vacuum tubes that need to be replaced by on-site technicians

Multi-stage chemical rockets launched dozens of solar powered geostationary satellites, each with multiple reflectors a few meters across that use high frequency spot beams and 50-100 W amplifiers to send hundreds channels of television to fixed receivers on the ground about 18 inches across.

Building and launching a satellite would be expensive, but it would be cheaper than building a ground based network to cover such a large area.

This overall concept is a remarkably accurate description of direct broadcast TV satellites built starting in the mid 1990s.

Only 50 W per channel would be needed to transmit TV to a parabolic receiver about a foot across. The satellite could send many transmissions using the same few reflectors.

Power could be provided by solar energy, but batteries would be required for an hour or so each day around the equinoxes.

Instead of an omnidirectional antenna, a reflector only a meter or so across could concentrate the beam on the hemisphere of Earth for radio waves of 3000 megacycles per second (we now call that “S-band”). Larger reflectors could produce a smaller beam to cover a single country or a smaller region.

A single satellite could cover almost half the globe. Three would be required for world-wide service, but “more could be readily utilized.”
Specific longitudes over Europe, Asia, and the Americas would be most suitable.

There was not yet any evidence that radio waves actually could penetrate the ionosphere, so this should be tested by a surplus V2 rocket (they had just become surplus a few weeks before!), or by bouncing radar off the Moon. (The US Army did both the following year.)

Reaching this orbit requires multi-stage rockets but is feasible with known propellants like oxygen and hydrogen.

A satellite in stationary orbit “could act as a repeater to relay transmissions to any two points on the hemisphere beneath using any frequency which will penetrate the ionosphere.”

A satellite in a specific orbit of radius 42,000 km, positioned over the equator, would rotate with the Earth and “would remain fixed in the sky of a whole hemisphere”.

Because the orbit appeared stationary, an antenna on Earth “once set up, could remained fixed indefinitely.”

Future television broadcast networks would be much harder and more expensive to build than FM or shortwave radio because high frequency signals don’t travel over the horizon.

New rocket technology could reach orbit “in a few more years”.

In 1945, Clarke was probably one of a handful of people on the planet who could design an orbit and a high frequency radio transmitter, even though he hadn’t yet been to college.

In his brief paper, Clarke explained the following points: