I am trying to understand how to choose a coaxial cable (for my current application, I need a 50Ohm coaxial cable that works reasonably well in the DC-10GHZ range).
According to the table in section "standards" of Wikipedia, I would choose the cable with the fewer possible "max attenuation", eventually taking into account the size and rigidity of the cable (I don't care about velocity factor). But I don't known if this attenuation measure at 750MHZ does mean something about 10GHZ.
More practical related question:
Does the LMR200 perform reasonably well at 10GHZ?
What about RG402? (I've read somewhere this is the preferred option for 10GHZ radio ham, but I don't understand why).
Best Answer
10GHz is very high frequency, and good cables for it won't come cheap. You will need to read the datasheets for specific cable products from specific suppliers.
The attenuation at 750MHz will not be a good indicator of performance at 10GHz.
The LMR200 you mention is not suitable. Note that the attenuation graphs and tables stop at 5.8GHz.
Generally thinner cable has higher attenuation loss. However, for any size of cable, there is a maximum frequency above which it will 'mode', that is, allow propagation of other modes in addition to the normal TEM coaxial mode. Above this frequency, all bets on any cable being well-behaved are off. This means that if attenuation is important to you, use the largest diameter cable you can that is still uni-modal at your top frequency.
RG402 is a 'semi-rigid' coax, rated up to 36GHz. This is the best value for money for cables within instruments where you don't need continual flexing. There are two principle sizes of semi-rigid used in instruments, '85thou', and '141', 0.085" and 0.141" outer diameter respectively. The thinner one is easier to bend by hand, but has higher loss than 141.