Thanks for the reply:
Well fortunately I have watched that video three times now and understand it. I never fly FPV by myself as im not comfortable with it not having a spotter. So in that case having a narrow field of view is not a problem because my buddy will be my "antenna tracker". 15km is what my ultimate goal is. And im almost certain that it will be extremely hard for me to reach that with 5.8Ghz but it can be done. If you look at my other started threads you will see exactly what my ground station looks like and my airframe. I get about 30 max flight time with it cruising at about 35-40km/h.
Get annother battery with to double your flight time. Also the antennas that you linked are called yagi's but they are not usable for human tracking. I bet that your friend cant track you when you are 2Km away! You would have to use a yagi. 2.4 GHz and 5.8 GHz wont give you 15Km range. So this is what i advice:
Learn about FPV. Just look arround on the forums! Google and search what other people use and what kind of results they are getting. Before getting into FPV you will have to learn allot about it. And please don't skip this step or you will and up with the wrong equipment.
Start cheap! Use your 5.8 GHz and 2.4 GHz to learn about FPV and different antennas. Build helicalls and CP antennas, this will teach you allot about FPV antennas.
If you still want to go long range buy 433MHz RC (EZuhf) and 2.4 GHz FPV lawmate 500mW. If you are going to use a yagi you will need an antenna tracker. This will cost arround 1000$ to fly 15Km. Also it's not legall to fly out of sight! I do it but I only do it with gear that I can trust. Also for these frequencies you will need a HAM licence to stay legal with your RC and FPV gear.
Allot of people are getting into (long range) FPV because they watch videos from trappy. Allot of people buy long range FPV gear and after flying about 20 times they are starting to get bored of flying long distances. It takes allot of time! Can you tell me more about your experience with FPV?