Source: Chinese language blogpost
The NASA Spaceflight article Queqiao relay satellite launched ahead of Chang’e-4 lunar mission describes the communications relay satellite that will be used to communicate with Chang'e-4, which will be on the far side of the Moon and therefore out of direct communications with Earth.
This tweet says:
And the 448 kg Queqiao Chang'e-4 relay sat before launch
and shows the images below, which show a folded dish antenna that looks to me to be much larger than I would have expected. There's an element of risk using a folded dish instead of a rigid one, and so this must have some substantial advantage.
Will this large dish be used to communicate with Earth, or Chang'e-4, or both? The reason I ask is that since the satellite in orbit around the Moon will be visible from a station on Earth for many hours at a time, a huge data rate would not be necessary, unless it were live video and couldn't be buffered. In that case though, how would it pick up signals from Chang'e-4 at the same time?
Question: Why does Queqiao (Chang'e-4 relay satellite) have such a large dish antenna? Will it be the largest dish ever on or near the Moon?
Below x2: Apollo 15 lunar Rover and Service Module. As @Hobbes points out the Apollo Service Module used four 78 cm dishes for Earth communication, and the Apollo Lunar Rover's antenna had a similar area. With advances in error correction low noise front ends and ground reception, it's surprising to see a much larger antenna used now. From here and here.