Comment by dhuk_2018
This goes back to the "olden days", we'd call them optics because there's a lens, an aperture, focus, waveguides, etc. Newer antennas actually DO have fiber optics (RF over fiber) conversion so you don't have to deal with waveguides and/or coaxial cables, just convert right to fiber at the feed.
You still need to deal with waveguides in modern design. A system like this will have OMTs (OrthoMode Transducers) and couplers made from machined / electroformed components that are essentially waveguide. If it has transmit capability it will have some kind of Diplexer made in a similar fashion. And of course, if it has transmit capability, there will be some kind of waveguide between the feed and the High Power Amplifiers (either Klystrons or Travelling Wave Tube Amplifiers). There's always some waveguide to serve as plumbing between the feed, these components, and others like the LNAs (Low Noise Amplifiers).
Most RF systems also won't convert right to fiber at the feed but have some kind of upconverter / downconverter assembly in the hub. Those converters might have fiber connectivity but more often than not it is some kind of intermediate IF frequency around the L/S-Band where the conversion to optical takes place separately.
While I am rambling on, I think the applications of this antenna will be very limited. The frequencies in use are generally speaking much higher now than they were 40 years ago (they picked up NSS-12 at 4 GHz, which is more or less DC these days). At lower frequencies you can get away with a lot of slop with regard to RMS surface accuracy and the like, but the Ruze equation is a harsh mistress and gain suffers considerably as frequencies go up. Modern antennas designed to work at higher frequencies will have a much better overall stiffness and surface accuracy, so you have more gain at the same diameter vs an old beast like this. All this is probably moot because an antenna feed like this designed for low frequencies won't even pass high frequencies.
The servo system is also another issue. They picked up a signal from a geostationary satellite which is as easy as it gets. If the satellite is inclined or (worse) in LEO / GEO, things get much tougher. And the higher the frequency, the tougher it gets because the antenna beamwidth is much tighter for a given diameter.