Thanks... that 75 Ohm was the fine print that many CCTV data sheets do not mention. It is just RG59 BNC. Possibly that means 75 Ohm.
Video (which is baseband) is always and always has been 75 ohm. RF stuff is usually 50 ohm (and usually narrowband) Everyone in the industry knows this. RG59 is 75 ohm, easy to look this up.
BNCs are the only connector I can think of that comes in both 50 ohm and 75 ohm forms, and they are not compatible, electrically or physically (you can force one into the other, this can distort the centre pin connection though).
And just for info. if there any white paper that talks about the quantitave signal degradation when using different methods to extend RG59 cables starting with the quick and dirty Splicing to the ultimate Crimped BNC ?
Depends on the max frequencies involved. Video is more demanding in that phase and amplitude variations with frequency make visible artifacts on vertical edges, and reflections cause ghosting. For RF narrow band all you usually care about is loss at one frequency and at high power the VSWR.
75 ohm was long ago chosen as lowest loss point for coax, and 30 ohm as highest power handling, and 50 ohm is a compromise value. 30 ohm flexible cable is difficult to manufacture so 50 and 75 ohm predominated.