Question: What kind of media station did the broadcaster Turaga Janaki Rani work with for two decades, which is a station which uses the technology of radio waves to carry information by systematically modulating properties of electromagnetic energy waves transmitted through space?

Context paragraphs:
Turaga Janaki Rani: Turaga Janaki Rani (August 31, 1936-October 15, 2014) was a broadcaster, social activist and a writer worked with All India Radio for two decades.  Popularly known as Radio Akkayya (Telugu: రేడియో అక్కయ్య Radio Sister).

Radio receiver: In radio communications, a radio receiver (radio) is an electronic device that receives radio waves and converts the information carried by them to a usable form.  It is used with an antenna.  The antenna intercepts radio waves (electromagnetic waves) and converts them to tiny alternating currents which are applied to the receiver, and the receiver extracts the desired information.  The receiver uses electronic filters to separate the desired radio frequency signal from all the other signals picked up by the antenna, an electronic amplifier to increase the power of the signal for further processing, and finally recovers the desired information through demodulation.

Parabolic antenna: A parabolic antenna is an antenna that uses a parabolic reflector, a curved surface with the cross-sectional shape of a parabola, to direct the radio waves.  The most common form is shaped like a dish and is popularly called a dish antenna or parabolic dish.  The main advantage of a parabolic antenna is that it has high directivity.  It functions similarly to a searchlight or flashlight reflector to direct the radio waves in a narrow beam, or receive radio waves from one particular direction only.  Parabolic antennas have some of the highest gains, meaning that they can produce the narrowest beamwidths, of any antenna type.  In order to achieve narrow beamwidths, the parabolic reflector must be much larger than the wavelength of the radio waves used, so parabolic antennas are used in the high frequency part of the radio spectrum, at UHF and microwave (SHF) frequencies, at which the wavelengths are small enough that conveniently-sized reflectors can be used.

Polarization (waves): Polarization (also polarisation) is a property applying to transverse waves that specifies the geometrical orientation of the oscillations.  In a transverse wave, the direction of the oscillation is transverse to the direction of motion of the wave, so the oscillations can have different directions perpendicular to the wave direction.  A simple example of a polarized transverse wave is vibrations traveling along a taut string "(see image)"; for example, in a musical instrument like a guitar string.  Depending on how the string is plucked, the vibrations can be in a vertical direction, horizontal direction, or at any angle perpendicular to the string.  In contrast, in longitudinal waves, such as sound waves in a liquid or gas, the displacement of the particles in the oscillation is always in the direction of propagation, so these waves do not exhibit polarization.  Transverse waves that exhibit polarization include electromagnetic waves such as light and radio waves, gravitational waves, and transverse sound waves (shear waves) in solids.  In some types of transverse waves, the wave displacement is limited to a single direction, so these also do not exhibit polarization; for example, in surface waves in liquids (gravity waves), the wave displacement of the particles is always in a vertical plane.

Radio telescope: A radio telescope is a specialized antenna and radio receiver used to receive radio waves from astronomical radio sources in the sky in radio astronomy.  Radio telescopes are the main observing instrument used in radio astronomy, which studies the radio frequency portion of the electromagnetic spectrum emitted by astronomical objects, just as optical telescopes are the main observing instrument used in traditional optical astronomy which studies the light wave portion of the spectrum coming from astronomical objects.  Radio telescopes are typically large parabolic ("dish") antennas similar to those employed in tracking and communicating with satellites and space probes.  They may be used singly, or linked together electronically in an array.  Unlike optical telescopes, radio telescopes can be used in the daytime as well as at night.  Since astronomical radio sources such as planets, stars, nebulas and galaxies are very far away, the radio waves coming from them are extremely weak, so radio telescopes require very large antennas to collect enough radio energy to study them, and extremely sensitive receiving equipment.  Radio observatories are preferentially located far from major centers of population to avoid electromagnetic interference (EMI) from radio, television, radar, motor vehicles, and other manmade electronic devices.

Antenna (radio): In radio an antenna is the interface between radio waves propagating through space and electric currents moving in metal conductors, used with a transmitter or receiver.  In transmission, a radio transmitter supplies an electric current to the antenna's terminals, and the antenna radiates the energy from the current as electromagnetic waves (radio waves).  In reception, an antenna intercepts some of the power of an electromagnetic wave in order to produce an electric current at its terminals, that is applied to a receiver to be amplified.  Antennas are essential components of radio equipment, and are used in radio broadcasting, broadcast television, two-way radio, communications receivers, radar, cell phones, satellite communications and other devices.

Radio wave: Radio waves are a type of electromagnetic radiation with wavelengths in the electromagnetic spectrum longer than infrared light.  Radio waves have frequencies as high as 300 GHz to as low as 3 kHz, though some definitions describe waves above 1 or 3 GHz as microwaves, or include waves of any lower frequency.  At 300 GHz, the corresponding wavelength is 1 mm , and at 3 kHz is 100 km .  Like all other electromagnetic waves, they travel at the speed of light.  Naturally occurring radio waves are generated by lightning, or by astronomical objects.

Radar: Radar is an object-detection system that uses radio waves to determine the range, angle, or velocity of objects.  It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, weather formations, and terrain.  A radar system consists of a transmitter producing electromagnetic waves in the radio or microwaves domain, a transmitting antenna, a receiving antenna (often the same antenna is used for transmitting and receiving) and a receiver and processor to determine properties of the object(s).  Radio waves (pulsed or continuous) from the transmitter reflect off the object and return to the receiver, giving information about the object's location and speed.

Radio: Radio is the technology of using radio waves to carry information, such as sound, by systematically modulating properties of electromagnetic energy waves transmitted through space, such as their amplitude, frequency, phase, or pulse width.  When radio waves strike an electrical conductor, the oscillating fields induce an alternating current in the conductor.  The information in the waves can be extracted and transformed back into its original form.

Radio spectrum: The radio spectrum is the part of the electromagnetic spectrum from 3 Hz to 3000 GHz (3 THz).  Electromagnetic waves in this frequency range, called radio waves, are extremely widely used in modern technology, particularly in telecommunication.  To prevent interference between different users, the generation and transmission of radio waves is strictly regulated by national laws, coordinated by an international body, the International Telecommunication Union (ITU).

Supporting paragraphs: Turaga Janaki Rani Radio
Answer: All India Radio