Most articles say that a radiowave is able to propagate itself beyond the horizon because it is reflected off by the ionosphere (and the Earth itself).
But do radio waves also get bent according to the Earth's curvature due to gravity thus transmitting beyond the horizon without need for the bounce effect?
Calculating the path that a light ray takes in a gravitational field is a complicated business, but for the special case of a light ray coming from infinity and escaping to infinity there is a convenient approximate formula for the angle, $\theta$, the light ray is deflected:
$$ \theta \approx \frac{4GM}{r_0 c^2} $$
Where $M$ is the mass of the deflecting object and $r_0$ is the distance of closest approach. If we feed in the mass of the Earth and set $r_0$ to the smallest value it can have (the radius of the Earth) we get a deflection of $\theta \approx 2.8 \times 10^{-9}$ radians, or about $0.0000002$ degrees.
So the gravitational deflection of any electromagnetic wave by the Earth is entirely negligable.
