Question by Omax: radio communication system design for a broadcasting company?
In order to design a radio communication system for a broadcasting company which rf signal and propagation mode i can choose? Which modulation technique and transmitter will be appropriate for that? And lastly how do i draw the complete diagram of my designed system.
A case study of a company would be good.
A case study of a radio broadcasting company would be good.
Answer by Ecko
I am a bit confused over the mix of terms, a radio communication system, but for a broadcasting company. Would that be a communication system the company uses internally, or is it a communication company, or is it meant to be the actual broadcasting system? I cannot see what the context is, what sort of system you are talking about.
Before designing a system some specifications are needed, which are about the eventual quality:
1) Bandwidth – range of frequencies to communicate.
2) Direction – one way, both ways, simultaneous, or one direction at a time.
3) Signal to noise. Average and worst case noise levels due to received signal power.
4) Operational reliability. All the time, 99% of the time, whatever is available.
6) Type of service, information type. Data, voice, sound program material, stereo etc., TV link.
7) Connected to? Telephone line, one channel or many, TV link, computer, hand microphone? Maybe it is a program line to carry program material to the broadcast transmitter? Maybe it is a broadcast transmitter, radio or TV not a communications system.
With that information the system design can start.
Most systems will use line of sight communication for reliability. With suitable sites this is unlikely to be more than 40km without repeaters.
A medium wave broadcast transmitter will be intended for ground wave communication, maybe 50-200km.
A HF transmitter will need different frequency and propagation modes at different times. Communication can be regional, national, global with suitable equipment, but is mostly no longer used as other systems take over.
Other considerations concern fading, reliability and distortion, due to multi-path signals.
This could be AM for local to regional broadcasts, FM for higher quality local broadcasts, SSB etc for HF communication. Line of site links tend to be FM or digital.
Transmitter power is determined by the range, antenna design, signal to noise, reliability against interference and fading. The antenna is an important part of the system, in both transmitters and receivers.
Most of the traditional radio broadcasting and communication, including medium wave AM, all kinds of HF, and even FM broadcasting and communication is becoming, or already is, obsolete as digital radio systems take over slowly but surely, in broadcasting and communications.
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