I thought I'd see what I got out of EZNEC for modeling the three antennas on the wifi router. I treated each of them as single wires at 2.452 GHz about 1m off the ground (not the floor). Each wire was 8 cm long (0.654 lambda) spaced 8 cm apart. Radiation pattern is directed perpendicularly to the plane containing the antennas, so I have two of them pointed down (the wifi router is mounted to the side of the desk) and one pointed off to the side (there's a power strip that gets in the way of it pointing down like the others)
After reading through some of the original documentation for NEC learning about the somewhat arcane input format (like MCNP, it can be pretty confusing at first), I'm liking how EZNEC simplifies and hides some of the complexity, but is still accessible if needed. When I start getting into building antennas, I might have to get a copy of it.