there was a contest (i think in the USA) for link-range a few months ago. the winning team did 85km at 11mbit/s, using 3m 50dBi dishes.
Wow, would they be accepting competition from Bulgaria? :-)
[we could even accept USA made antennas]
We get much better results with much better smaller antennas.
For example: (real world link), 83km, 1.2m at one side, 1.8m at other (link rate limited to 24mbps to avoid RTT fluctuations)
That link routinely carries 11-12 Mbps (because the next in chain is limited to 10Mbps FDX radio)
On the topic: Indead cable lenght is major issue, as is cable quality. Amplifiers generaly do not improve wireless links - not only because of aplifying noise, but because amplifiers are not linear - while many do claim they are - truth is you can't get much quality at the price they are offered!
Another thing is, that it may not be legal to use high EIRP in most countries in these frequencies - I believe especially in Europe the 5GHz band is for lower power devices.