Hello all 
My 1st post 
Does anyone know the Polar Patten of the internal ariel on an AR300M?
I need it to “Beam” down a long but narrow corridor in both directions and wonder should I mount it flat on a shelf or vertical.
If vertical would I place the front and back faceing up and down the corridor?
All the best, Andy
The router’s internal antenna isn’t directional antenna. You can place it casually.
What a distance do you want? It can reach about 80 meters.
You can see the antennas on the PCB at GL-AR300M Series - GL.iNet Docs
The are cross-pol, which is good for diversity, generally increasing robustness of connections over the covered area. Being physically small compared to the wavelength at 2.4 GHz (~12 cm) there won’t be much directionality to the pattern, as kyson-lok indicates.
I would suggest not placing the router on or near (under ~10 cm) a metallic or conductive shelf or object, with ~30 cm potentially being better. RF can be very non-intuitive, so checking the signal strength where it matters to you is the best way to see if “tweaks” in location help or hurt.
The trace antennas are low gain - which is actually a good thing considering - it’s the gain of the antenna that helps determine the pattern.
How big/small the antenna is isn’t really a concern, it’s the gain - higher the gain, the flatter the pattern.
My they are small…
Thanks for the tip about distance from metal surfaces. That factor is quite relavent in this case.
Kind regards, Andy