Originally Posted by engineer(retard)
My distant recollection is that aperture directional gain makes up part of the Rx gain.
True - I was focussing on the "Tx power ** 4" bit. You can do cute stuff with the same-sized antenna to give you better directional gain (see "not all of the elements will radiate with the same power"); but I was focussing on what I thought was a "if you want twice the range you need 10x aperture" argument from the original poster.