[MLB-WIRELESS] External aerial, what cabling?

[Zoe Marshall]

I am in the process of gathering components to mount an aerial on the roof . 
I'm relatively new to wireless networking, but i've done my homework 
regarding coaxial cabling and found that the cabling I should be using is 
CDF-400 / LMR-400 or uncommonly, RG-213.

I need to run a 7-9 metre run of this cable, however which cable I am unsure 
of. I have found premade cables this size to be rather expensive. Are there 
any cheaper alternatives to the coax types I listed above which will do the 
job just as well with low loss, or perhaps somebody could direct me to where 
I may be able to acquire a cheaper premade cable?

Thanks,

Zoe