If you have a 50 ohm coax which is specified for 1.2GHz operation and which is terminated by 50 ohm resistor, the signal generator (transmitter) will see 50 ohm resistive impedance. If you want to double check, just measure the impedance using a VNA or spectrum analyzer+tracking generator+rf bridge.

Yea, and to be safe i'll make cable multiple of half wavelength long (taking into account velocity factor) so CI DOES NOT REALLY MATTER, since load impedance repeats at half wavelengths down the TL.

Sorry, but that's not quite so!

All is rosy at the input end of the cable, except that, using your figures, you still have a matching problem between 50 Ohms & 14 Ohms.

At every other point of the cable, apart from the halfwave points, the impedance looking towards the load is different than 14 Ohms.

For instance, at 1/4 wavelength back from the termination, the impedance is 401 Ohms, again using your figures.

You are still transferring the same power, so at that point, the line current will be low, and the voltage across the line, high.

This can, at high power levels cause dielectric breakdown, damaging the cable, as well as being a source of losses.

That is for a point where the impedance is purely resistive.

At other points along the cable the impedance may be highly reactive, causing large variations in both voltage & current.

High currents introduce greater I^2R losses, & as above, high voltages can cause losses or perhaps, break down.

For these reasons, the simple use of half wavelength transmission line is not widely recommended, especially using normal flexible coaxial cable.

Hams often "get away with it" by using Open Wire Parallel line, as its air dielectric, wide spacing, & low series resistance, allow the user to ignore to a large extent, the problems referred to above.