4.2. PARAMETERS OF ELECTROMAGNETIC WAVES

Electromagnetic waves travel with a VELOCITY of 300 000 km/sec. The FREQUENCY of radiowaves (oscillations per second) can be between 100 000 Hz and 300 000 000 Hz (100 kHz to 300 MHz). KEEP IN MIND there is a MINIMUM FREQUENCY of at least 30 kHz, only oscillations above this minimum are propagated. The AMPLITUDE is the maximum amount of electric field or magnetic field reached per one cycle. Electromagnetic waves have obviously two components the electric and the magnetic part, both are positioned at 90° to each other. After leaving the aerial the direction of both components is not changed, this means, we will receive the same waves under the same direction as they are transmitted. The way how the waves are produced (concering the direction of the components) is called their POLARISATION! Knowing this fact, we can easily understand why the reception can be improved by the direction of the aerial.