I know that radio waves occupy the lowest portion of the EM spectrum and gamma rays occupy the highest. I'd like to know if increasing the frequency of a radio wave can produce visible light and maybe eventually, gamma rays. I've searched a bit but couldn't find any definite answers. Are all the separate radiations distinct (can only be gotten from separate sources), or can you obtain them from each other by raising or decreasing the frequency as you need to? Are there limits to how high you can raise RF frequency (in cables, free space, etc)?