I think if you were to radiate out from any point inside of an enlarging circle, enlarging at the same speed as that circle, I can't see how it would radiate aw

I think if you were to radiate out from any point inside of an enlarging circle, enlarging at the same speed as that circle, I can't see how it would radiate away from that bubble. That said, the signal would be much stronger if you tuned it for specific regions of space.