Best answer by Sophia
Best location would be near a window... and they don't need to be a certain distance apart (ours are side by side).
But Chad has a point, even though it seems as if you're still using a landline, in actual fact you are not. It could be that your handset worked perfectly fine with a genuine landline, but becomes moody with the new line... especially if it's an older model.
It might be worth it to try it with a newer handset, or take your hub to the store (along with your handset) to have both tested.
Hope you get it sorted