VHF and UHF signal line-of-sight propagation distance calculator_online calculation tool

VHF and UHF signal line-of-sight propagation distance calculator

High frequency (VHF, also known as meter wave) in China is in the frequency range 48.5MHz ~ 223MHz

UHF (also known as decimeter wave) in China's frequency range is 470MHz ~ 806MHz

Short-wavelength (HF-segment) radio signals below 30MHZ rely on the reflection of the ionosphere for
long-distance propagation. The distance of propagation can range from hundreds of kilometers to tens
of thousands of kilometers. Due to the particularity of the ionosphere itself, the ionosphere is normally
high. The reflection of the radio signal at 40 MHz is very weak, and most of the signal will penetrate
the ionosphere and enter the space. Therefore, under normal circumstances, radio signals above 40 MHz
are basically transmitted in a straight line, and the distance of propagation is generally within one
or two hundred kilometers, which is what we often say in the "line of sight" range.

However, under the special conditions of the ionosphere and the atmosphere (troposphere), VHF and UHF signals
over 40 MHZ can travel hundreds of kilometers along the earth's surface. We usually call this kind of
transmission beyond the "horizon" as long-distance transmission. Sometimes, the radio signals in the VHF
band can also be reflected by the special conditions of the ionosphere and spread thousands of kilometers
away. This kind of propagation can be called ultra-long-distance propagation. The mechanism of radio wave's
"horizon" propagation, long-distance propagation and ultra-long-distance propagation are different. The
following refers to the use of common receiving equipment (ordinary radio, receiver, ordinary antenna) to
receive radio signals from distant stations and local radio signal intensity is not much different.