Chirp is a easy to use programing software for RF/UHF radios.

(Chirp Programming Software).

This is a simple and well made video to help understand Line of Sight radio communications.

This is a good video that give you an easy to understand theory on Antenna Gain DBI.

Good basic video, to help understand how a radio repeater works...

Good video, I actually used this design to build my GMRS 1/4 wave ground plane Antenna! I found the 1/4 wave to be the Best and Cheapest antenna to build for a DIY project...