In the recent article Flightradar24 gears up for a new wave of flight tracking I've read about FR24's experimental Wave Glider ADS-B receiver - essentially a self-propelled, solar power buoy as a remote ground station.
What do the radiation patterns of ADS-B transmissions on large airliners tend to look like? In particular, the transmissions that would be received by satellite or surface ADS-B receivers collecting traffic information.
Are there any examples of these radiation patterns published? Are there guidelines, best practices or regulations that apply to the directionality of the radiation?
An example of a general requirement might be EASA's CS-ACNS:
CS-ACNS.D.ELS.060 Antenna installation
(See AMC1 ACNS.ELS.)
(a) The installed antenna(s) has (have) a resulting radiation pattern which is (are) vertically polarised, omnidirectional in the horizontal plane, and has (have) sufficient vertical beam width to ensure proper system operation during normal aircraft manoeuvres.
(b) Antenna(s) is/are located such that the effect on the far field radiation pattern(s) by the aircraft structure are minimised.
which only addresses directions above/below horizontal to the extent that they apply to "normal aircraft maneuvers." There may be more.
Below I've added a similar but different gain pattern as an example of the kind of data I am looking for. However it is the gain pattern for a downwards-looking ADS-B receiving aboard a satellite, showing good reception from below (nadir: $\theta,\phi \approx 0 $). What I am looking for is a similar type plot, but for the radiation from an aircraft.
above: Photo of FR24's ADS-B receiver aboard a Liquid Robotics Wave Glider platform. Photo credit Flightradar24.
above: Example from this paper of an receiver's gain pattern. In this case it is an ADS-B receiving antenna system, aboard a satellite, showing gain optimization looking straight down (nadir).