Macbook air wifi problem when is on my legs

I've a strange problem with my macbook air. When I use it on my legs, wifi doesn't work or disconnects. I need to raise up the mac in order to get the signal. I'm in a small flat and the signal is very strong. Anyone has got a similar issue?

thanks

UPDATE 1

It seems the position won't cause the problem, but using a ping command through automator will help to not disconnect.