I wrote:

Some thoughts:

o Line of site is out. Dist to horizon for tower ht h earth radius R
is sqrt((R+h)^2-R^2) or sqrt( 2 R h + h^2 ), effectively sqrt( 2 R h ).
For units of miles sqrt(2 R) is approx 90 and sqrt(2 R h) is the same.

Insert at end of sentence: "for h=1" ^^^^^

So for two towers a mile high, each is 90 mi from horizon for a
total of 180 mi. For ht of 0.1 mi (528') each, get 180 * .316 or
about 57 mi total.