How VHF signals travel in straight lines, why height matters, and why reflections can fool you.
What you will be able to do
Define line-of-sight propagation
Say which frequencies follow a straight path
Explain why repeaters are high and how to extend 2 m range
Explain why a signal aimed at a mountain may be heard elsewhere
Why does height matter so much on VHF?
VHF signals normally travel in straight lines, and that changes how you plan.
Line of sight
Line-of-sight propagation is when the signal travels in a straight line from the transmitting
antenna to the receiving antenna.
Radio waves usually follow a straight-line path at VHF and higher, for example on 2 m.
Two antennas on a curved Earth: the higher one sees farther, and a mountain blocks the path
Height gives range
The two-metre range depends on the elevation of the transmitting and receiving antennas.
To talk significantly farther on 2 m, raise your antenna.
VHF repeaters are placed at high elevations so their line-of-sight signals travel farther.
Reflections
VHF and UHF signals are easily reflected by objects in their path. This is why a signal aimed
at a mountain can be heard in a different direction: it bounces off the mountain.
You now know
Line-of-sight signals travel in a straight line from transmitting antenna to receiving antenna.
VHF and higher, such as 2 m, usually follow a straight-line path.
Raise your antenna to extend 2 m range; repeaters sit high for the same reason.
VHF and UHF signals are easily reflected, so they can be heard in unexpected directions.