The highest frequency which a conventional vacuum-tube oscillator can generate is not limited by the
Answer: Degree of emission from the cathode
Microwave frequencies are normally regarded as those in the range of
Which of the following is used as an oscillator device in the SHF band?
What is the purpose of the electromagnetic field which surrounds a traveling-wave tube?
Answer: To keep the electrons from spreading out
A traveling-wave tube (TWT) amplifies by virtue of
Answer: The absorption of energy by the signal from an electron stream
A high-power microwave pulse of the order of megawatts can be generated by a
Coupling into and out of a traveling-wave tube can be accompanied by a
At what position is the input signal inserted into a traveling-wave tube?
Answer: At the cathode end of the helix
The cavity resonator
Answer: Is equivalent to an LC resonant circuit
A shipboard equipment which measures the distance between the ship’s bottom and the ocean floor.
In microwave transmission using digital radio, what causes most intersymbol interference?
Answer: Delayed spreading
Which causes multipath or frequency-selective fading?
Which of the reception problems below that is not due to multipath?
What do you call an attenuation that occurs over many different wavelengths of the carrier?
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.
Rainfall is an important factor for fading of radio waves at frequencies above
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)
If k-factor is greater than 1, the array beam is bent
Answer: towards the earth
Calculate the effective earth’s radius if the surface refractivity is 301.
__________ is the progressive decrease of signal strength with increasing distance.