Very High Frequency
Frequencies ranging from 30 MHz (30,000
kHz) to 300 MHz (300,000 kHz) are defined as Very High Frequency. One important
characteristics of this spectrum is that they are not readily reflected by the ionosphere
limiting their range of communication to the line of sight (the same reason restricting
the range of coverage of transmission from a TV transmission tower). This implies
that taller is your antenna, further is the distance travelled by the radio signals
transmitted from your radio transmitter. Very High Frequencies provide the most reliable
short distance line-of-sight radio communication which is free from the control of other
atmoshpheric effects. There are different atmospheric effects like that of due to the
generation of patches of high ionization sporadicE-Clouds around the equator or other
freak atmoshpheric phenomenons like temperature inversion and tropospheric ducting which
extends the range of VHF communication beyond the line-of-sight. Ham radio operators are
alloted the frequencies ranging from 144 MHz to 148 MHz (in India it is 144 to 146 MHz)
and a limited frequencies in the 50 MHz range.VHF equipments can be
designed compact in size which makes them handy during mobile operation. Either Passive or
active relay stations are used to relay VHF signal to far away places.