Question:

(a) A HF digital radio data link operates over a distance of 1000 km. Depending on transmission frequency, reflection can occur from the F2 region of the ionosphere at a virtual height of 320 km where the electron density is 1.3 x 10¹² el/m³ and from the E region at a virtual height of 110 km where the electron density is 1.2 x 10¹¹el/m³.

(i) What is the Maximum Usable Frequency (MUF) for the path?
(ii) Over what transmission frequency range will there only be an F2 region reflected path?
(iii) When both E and F region reflected paths occur together, estimate the maximum advisable bit rate by determining the difference in time delay between the two paths.

(b) Ionospheric propagation delay introduces errors in range-finding by satellite navigation systems such as GPS. Determine the extra time
delay (compared with free space propagation) and hence, the range error at the GPS frequency 1227.6 MHz for a path through the ionosphere at an angle of 70^o to the vertical.

The electron density of the ionosphere is given by a constant 3 x 10¹¹el/m³ from 200 to 400 km height and zero elsewhere and the velocity c is 299,792,458 m/s.