I thought that LOS and VLOS is the same but I found this in some websites:
Radio LOS Is Not the Same as Visual LOS
SG 2nd Edition
With visible light, visual LOS (also called simply ?¡é?€??LOS?¡é?€??)
so what is the different between: LOS and VLOS ?
Visual LOS is just as it sounds. If you can see one antenna from the other antenna, you have visual LOS.
Radio LOS is different because of something called the Fresnel (FRA-nel) zone. Do a search on this and you will find lots of articles. A good baseline article would be at wikipedia.org.
The low down is that even if you can visually see your other antenna, there could be obstructions that will block the first Fresnel zone (1FZ). There are Fresnel zone calculators on the Internet that will let you know how large the Fresnel zone is, depending on the radio frequency and distance between antennas.
Read up on it, and let us know if you have any more questions.
it is clear now.
One is never too old to learn.
Practice makes perfect.\\