What I'm confused about, is why if this is the correct stuff to use do all the kits on Amazon, eBay etc use RG6 cable? From what I can see NX100 is cheaper so it's presumably not cost.
It is cost.
It's also relying on consumer ignorance.
The 'RG'-bit of RG6 stands for Radio Guide. It was an idea by the military to classify cables. Officially, RG classifications are obsolete, however, they've been in use since WWII and so they've stuck.
Since the classification guide is now defunct, there's no guarantee beyond some basic physical characteristics what the performance of an RG6 cable might be. All it really describes now is a general application (eg suitable for TV and satellite signals), the impedance of 75 Ohms, and then some sizes such as the core diameter, and the thickness of the inner insulation (the dielectric), how many layers of shielding it has, and the overall diameter.
RG-6 is, loosely speaking, a 6.6~6.8mm diameter cable. This means that WF100, TX100, PF100, NX100 are all RG6 cables. However, they're a world away in construction, performance and longevity compared to basic RG6.
If we compare Webro WF100 to the sort of basic RG6 sold on Ebay then you'll start to see the differences.
Webro WF100:
Centre core - solid copper
1st layer of shielding - copper metal foil
2nd layer of shielding - copper braid with >40% coverage
Low grade RG6:
Centre core - steel with an anodised outer coating of copper (CCS - copper coated steel)
1st layer of shielding - plastic with a deposited aluminium coated
2nd layer of shielding - aluminium braid with substantially lower coverage than 40%
In terms of electrical performance there are some differences. The DC resistance is higher, as is the signal loss (attenuation) which gets worse as the frequency increases, but all cables have losses. The thing is though, for fairly short runs of under 20m, you'd be hard-pressed to notice any real difference.
Where things start to go very wrong for RG6 is as the cable ages. The PVC jacket tends to be more susceptible to weather and UV damaged. It cracks and lets in water. This then eats the aluminium braid and eventually you lose what's left of the shielding and before crapping out altogether as the return signal loses connection.
Buy decent quality cable. Going cheap is a false economy.
