CLASSIFICATION OF RADIO TRANSMITTERS ACCORDING TO THE TYPE OF SERVICE INVOLVED
CLASSIFICATION OF RADIO TRANSMITTERS ACCORDING TO THE TYPE OF SERVICE INVOLVED:
1) Radio Telegraph Transmitters: A radio telegraph transmitter transmits stele graph signals from one radio station to another radio station. It may use either amplitude modulation or frequency modulation. When point-to-point radio communication is involved, the transmitting antennas are highly directive so that the electromagnetic energy is beamed into a narrow beam directed towards the receiving antenna at the receiving radio station.
2) Television Transmitters: Television broadcast requires two transmitties one for transmission of picture and the other for transmission of sound. Both operate in very high frequency of in ultra high frequency rang. The picture transmitter is amplitude modulated by the picture signal occupying a band of about 5 5MHz Vestigial transmission is used i e one full sideband and only a vestige or a part (about 0 75 MHZ) of the other sideband together with the carrier are radiated from the transmitting aerial. The total bandwidth occupied by one television channel is about 7 MHz. The sound carrier is frequency modulated.
3) Radar Transmitter: Radar (abbreviation for Radio Detection and Ranging) may be of two types:
(i) Pulse Radar and
(ii) C.W. (Continuous Wave Radar).
Pulse radar transmitter uses pulse modulation of carrier. It uses high output power typically 100 kW peak and operates at microwave frequencies typically 3000 MHz (10 cm wavelength) or 10,000 MHz (3 cm wavelength). The C.W. radar transmitter may use frequency modulation of the carrier voltage or may utilize Doppler Effect.
4) Navigation Transmitters: A number of navigational aids using special types of radio transmitters and receivers are used these days for sea and air navigation. Also radio aids are used for blind landing of aircrafts. Typical radio aids of landing are (a) I.L.S. (Instrumental Landing System) and (b) G.C.A. (Ground Controlled Approach). In addition to these, several other radio means are provided at air port for surveillance. Accordingly a large number of radio transmitter of varied types, frequency and power are required depending upon the operation desired.