|Radio and Electronics (DED Philippinen, 66 p.)|
|2. PRINCIPLES OF RADIO COMMUNICATION UNICATION|
There are two people who want to communicate with each other but the distance is too far... WHAT CAN BE DONE?
A very old fashioned way to solve this problem was to send a MESSENGER.
Since about 100 years there is a more convenient method of communication: the TELEPHONE.
Since about 50 years there is another - even more convenient method of communication the RADIO TECHNOLOGY.
Since the PROPAGATION of SOUND is very limited in distance for communication across longer distances another means of transporting the SIGNAL is necessary.
As we are reminded to by the sketches above, COMMUNICATION SYSTEMS have been developed step by step through the last century.
All those different technologies are working in between the two ends of the original way of communicating.
Even the most modern communicationsystem is working on the same overall system:
FIRST: there has to be a method to translate sound (air vibrations) into an ELECTRIC OSCILLATIONS (current or voltage oscillations).
SECOND: there has to be a method to transport this electric signal across huge distances Either by wires or by so called ELECTROMAGNETIC WAVES (also called RADIOWAVES)