Guys, lots of questions coming in regarding HF vs. UHF/VHF radios and antennas. Let’s flog that deceased equine a little longer; If you get your Amateur license at the Technician level, you won’t have to ask these questions any longer.
VHF/UHF radios work on the frequency bands that inherently use short/very short antennas, plus, they are usually very small, light weight, easy to operate, and run off of batteries. What’s not to like! I think this is why most folks initially purchase these radios as inter-squad level comms.
And while they do have those advantages, one of their major disadvantages is that they usually only work when they are in unobstructed view (line-of-sight) of one another. Put most any obstruction between the two (an area known as the First Fresnel Zone) and you have no or very poor comms. The obstruction could be just about anything; a hill/mountain, forest, large buildings, moving vehicles, or any combination of these things. In addition, factors such as power output and receiver sensitivity are also in play.
So, how do we get around (or over) those obstructions? Use a repeater mounted above the obstruction. Then you are relying on someone Else’s infrastructure. And if you do get comms over the mountain to your buddy in the next valley, how do you get to the valley beyond him? Another repeater.
Here is the link for a well put together article on comms for the beginner from INFORMOPS. Take a look toward the end of the article for some visual descriptions of the challenges regarding VHF/UHF comms. I should have had his blog listed as one of my favorites a while back, my mistake. HT to PSYOP Soldier for reminding me.