Talk:Tutorial:Ideal Orbits for Communication Satellites
It's necessary to use more than 3 satellites to maintain line of sight between them if the planet is too large. Using greater than 3 satellites in a circular constellation can provide the advantage that all of the coverage area of the network can be kept above the planet surface and is therefore potentially useful. The network from such a constellation reaches slightly deeper into space, so could be preferable early in the game when antenna communication range can limit mission possibilities.
The 4-satellite constellation section mentions two different formations, but the distance management section and linked KSP ComSat altitude spreadsheet only provide one set of 4-satellite specifics. The 4-satellite constellation sections spends significantly more time describing the tetrahedral formation rather than the circular one, which is described as being essentially the same as the 3-satellite configuration. This makes it very easy to assume the provided details are for the tetrahedral formation, when in fact they are for the circular one.