In SpaceX's Echostar XXIII Hosted Webcast after
T+ 00:03:50 they mentioned the "re-radiation system" as a part of the payload fairing that increased it's value and possibly added to the benefit of recovery of the fairing post-launch, rather than just "ditching it".
What is it, why is it so valuable, and why wouldn't just a low tech, low cost, not-worth-mentioning-in-the-video solution like a little piece of coax with a dipole on each end be enough? Any radios on the satellite would be optimized for strong outgoing and weak incoming signals as they would be in orbit tens of thousands of kilometers away from a ground station, so just some weak coupling would be enough for communication over a distance of few tens of meters.
edit: An example of an RF window (another alternative solution) is described in Section 4.1.3 of Proton Launch System Mission Planner’s Guide; SECTION 4; Spacecraft Interfaces.
note: The video is set to start at 21:29 (
T+ 00:03:30) so you can see the fairing separate. The re-radiation system of the fairing is mentioned after another 20 seconds or so.