I found a component (HA-5002) that's like perfect for my application.
Heres the datasheet: http://www.intersil.com%2Fdata%2Ffn%2Ffn2921.pdf
The datasheet states it is a current buffer, ie unity gain gain amp.
Ok thats fine expect I need to take a signal and transmit it over a coaxial cable and get the same output after the input and output loads. In this case both are 75ohms so I have to drive two 75ohm resistors in series. Similar to the example given (Unity Gain buffer.png attached, which is at top of page 6 of the datasheet), except they use 50 ohm resistors. They show a scope trace where Vin = Vout.
As I see it Rm, and RL make a potential divider with Vout halfway in between, surely Vout = 1/2 Vin? The datasheet clearly shows otherwise.
I even simulated it (simulated.png attached) and got the result I expected, Vout = 1/2 Vin because of the potential divider network. PS the green trace is the output.
I can't see what I am overlooking? Is it some transmission line magic?