To be honest, I wouldn't use a beam for the transmitter. I would use an omnidirectional antenna. Depending on the antenna, some beams are pretty tight and you could lose the airplane. I'd pick up a cheap Antron or something. You can find AM radios fairly cheap that operate in the 27.415 - 27.555 range. The antron would work great. You can hook an external antenna to the transmitter, but you'd have to play with the length of the coax to get the SWR just right. The radio already has a matching unit built in, so I wouldn't recommend using an external one.
I have video on one of my planes, but the best shots I get are from a 2 meter glider at 500 - 700 ft. You can see a long ways off from that high. I've never dabbled in going beyond my line of sight. I was never comfortable leaving an expensive plane in the hands of electronic fate. If the plane were to go down for some reason, like over a wooded area, I could probably tell which tree it was in, and not have any idea where that tree is.
My question to you is why use HAM for video? I haven't kept up since I got out of the whole HAM thing, but you can get equipment now that you don't have to have a license for, and is really light. My biggest concern would be the weight of the transmitter plus the power supply. You can get a nice $200 set up with the receiver plugged in to a monitor right in front of you. You could retransmit that signal over HAM if that's what you were going for.