Theoretically electromagnetic radiation field strength varies in inverse proportion to the square of the distance, but when atmospheric attenuation effects and the absorption of the terrain are taken into account the attenuation can be as high as the inverse ___________ power of the distance.

Coupling into and out of a traveling-wave tube can be accompanied by a

A. Waveguide match

B. Cavity match

C. Direct coax-helix match

D. All of the above

When it is desired that short-range targets be clearly seen on a pulsed-radar set, it is important that the receiver and display system have

A. A long time constant

B. Low-pass filters

C. The shortest possible time

D. The restricted high-frequency response

The antenna separations (in meters) required for optimum operation of a space diversity system can be calculated from:
where R = effective earth radius (m) and L = path length (m)

A. $${\text{S}} = \frac{{2\lambda {\text{R}}}}{{\text{L}}}$$

B. $${\text{S}} = \frac{{3\lambda {\text{R}}}}{{\text{L}}}$$

C. $${\text{S}} = \frac{{\lambda {\text{R}}}}{{\text{L}}}$$

D. $${\text{S}} = \frac{{\text{L}}}{{\lambda {\text{R}}}}$$

The aquadag coating on the inside of PPI tube is used

A. To focus the beam of primary electrons

B. To shield the electron beam from unidirectional magnetic

C. As a second anode and to prevent the build-up of secondary field

D. All of these