The '433MHz' they quote IS used by many A/V senders, just not for the video/audio signal
It's a utility RF link for carrying remote control signals from the Rx to Tx, so you can transmit the signal from a DVD player downstairs and still pause/ff/rw etc...
It is misleading, and it gets my blood up when I see 'Digital TV A/V sender!' when its just a standard analogue sender, but with a scart socket for the input, instead of RCA, and even then, scart is still analogue (despite a 12 minute argument with a bloke in Dixons, fool). Still, we're engineers here, we know different
To the OP, as I said before, a directional antenna would add a fair bit of gain, and I tihnk you may be able to add in an RF amp providing you don't go over the top, and that your antenna's are very direcitonal, I still say 2km is possible with these modules.
Try **broken link removed**
I have the smallers ones, but my app is portable.
Blueteeth
PS. just realised I repeated what nigel said, sorrry