Here Albert Helfrick speaks about 40% modulation depth for each tone in a localiser radio signal. However latest manuals of ILS manufacturers and google source speaks about 20% modulation depth, not 40%. Albert also says that modulation depth becomes 20% at the centreline of runway.
My question is whether Albert is correct or manufacturers like NORMARC, Thales and SELEX are correct? If Albert is correct then how does 16,20,24 element log periodic dipole array help in achieving this modulation depth variation?
I would appreciate if someone with proper explanation comes up. And this question is not duplicate so please do not confuse it with other modulation varying behaviour of questions asked on this forum.