The formula of range of transmitting signal for a TV program for a transmitting antenna in terms of the height of the antenna and radius of the earth is, 
$d=\sqrt{2R_{e}h}$, here $R_e=6.4\times {10}^6 \mathrm{m}$ and $d=64\times {10}^3 \mathrm{m}$, 
it means, 
$h=\frac{d^2}{2R_e}=\frac{{\left(64000\right)}^2}{2\times 6.4\times {10}^6}=320 \mathrm{m}$